Overview
Every number RefinanceUSA displays is produced by a deterministic mathematical formula applied to your inputs. There is no machine learning, no black box, and no lender-influenced model. This page documents every formula we use, the assumptions behind each default value, and the known limitations of each calculator.
RefinanceUSA is not a lender. Results are estimates for comparison and educational purposes only. Actual loan terms, closing costs, and savings depend on your specific lender, credit profile, and local fees. Always review your lender's official Loan Estimate before making any refinancing decision.
Monthly Payment Formula
All monthly principal-and-interest (P&I) payment calculations use the standard fixed-rate amortization formula used by every lender and mandated by CFPB Loan Estimate disclosures:
Where:
M = monthly payment
P = loan principal (balance)
r = monthly interest rate (annual rate ÷ 12 ÷ 100)
n = total number of monthly payments (term in years × 12)
When the interest rate is 0%, the formula simplifies to M = P ÷ n.
What is not included: This is the P&I payment only. It does not include property taxes, homeowners insurance, PMI, or HOA dues. Your actual total monthly housing payment will be higher.
Break-Even Calculator
The break-even calculator answers: how many months until your monthly savings fully recover your refinance closing costs?
Formula
Monthly Savings = Current P&I Payment − New P&I Payment
Inputs
- Current balance, rate, and remaining term — used to calculate your current P&I payment
- New rate and term — used to calculate the proposed new P&I payment
- Closing costs — you can enter your lender's actual figure from the Loan Estimate, or use the calculator's estimate of 2% of the new loan balance
Closing Cost Default
When you leave closing costs blank, the calculator defaults to 2% of the new loan balance. This is a conservative midpoint estimate based on CFPB data showing typical refinance closing costs ranging from 1.5% to 3% of the loan amount nationally. Your actual costs may be higher or lower depending on your state, lender, loan size, and whether you pay points.
Key assumptions:
• Fixed-rate loans only. ARM-to-fixed or ARM-to-ARM comparisons require adjusting inputs for the new fixed period.
• Break-even does not account for the time value of money (NPV). For a rigorous financial comparison, discount future savings at your opportunity cost rate.
• Tax deductibility of mortgage interest is not factored in. Consult IRS Publication 936 and a tax professional.
Mortgage Savings Calculator
The savings calculator compares total interest paid over the full remaining life of your current loan versus the proposed new loan.
Formula
Net Lifetime Savings = Total Interest (current loan) − Total Interest (new loan) − Closing Costs
Amortization
The calculator runs a full month-by-month amortization schedule for both loans rather than using a shortcut estimate. Each month: interest = remaining balance × monthly rate; principal = M − interest; new balance = old balance − principal.
Key assumptions:
• You keep the new loan for its full term. If you sell or refinance again before the term ends, net savings will differ.
• Closing costs are assumed to be paid upfront, not rolled into the loan. If you roll costs into the new balance, add them to the principal input.
Loan-to-Value (LTV) Calculator
The LTV calculator computes your current equity position and shows where you stand relative to key LTV thresholds.
Formula
Equity ($) = Current Home Value − Remaining Loan Balance
Equity (%) = 100 − LTV (%)
Key LTV Thresholds
| LTV | Significance |
|---|---|
| Above 97% | Generally ineligible for conventional refinance |
| 97% | Maximum for most conventional rate-and-term refinances |
| 95% | Some lenders' maximum; HIRO/FMERR high-LTV programs have different rules |
| 90% | Maximum for VA cash-out refinance (full entitlement) |
| 85% | Maximum for FHA cash-out refinance |
| 80% | Maximum for conventional cash-out; PMI no longer required below this level |
| 78% | Automatic PMI cancellation required under the Homeowners Protection Act |
PMI Removal Calculator
The PMI removal calculator estimates how many months until your loan balance naturally amortizes to 80% LTV, and what a lump-sum paydown would cost to reach that threshold immediately.
Formula — Months to Removal via Amortization
PMI Removal Month = first t where Balance(t) ≤ Home Value × 0.80
Formula — Lump-Sum Paydown
PMI Rules (per Homeowners Protection Act)
- At 80% LTV: You can request PMI cancellation. Lender may require a current appraisal and good payment history.
- At 78% LTV: PMI must be automatically cancelled by the servicer (for loans originated after July 29, 1999).
- Midpoint of amortization: PMI must be cancelled at the scheduled midpoint of the loan term, regardless of LTV, for conforming loans.
Cash-Out Refinance Calculator
The cash-out calculator estimates how much cash you can access, what your new loan balance and monthly payment would be, and whether the refinance makes financial sense.
Maximum Cash-Out by Loan Type
| Loan Type | Max LTV (Cash-Out) | Source |
|---|---|---|
| Conventional | 80% | Fannie Mae / Freddie Mac guidelines |
| FHA | 80% | HUD Handbook 4000.1 |
| VA | 90% | VA Lenders Handbook, Chapter 6 |
| Texas (any type) | 80% | Texas Constitution, Article XVI, Section 50(a)(6) |
Formula
Max Cash Available = Max New Loan − Current Balance − Estimated Closing Costs
New Monthly Payment = amortization formula on New Loan at New Rate for New Term
Key assumptions:
• The calculator uses 80% LTV as the default maximum for conventional cash-out. If you have VA eligibility, adjust for the 90% VA limit.
• Closing costs are estimated at 2% of the new loan balance if not entered manually.
• Texas homeowners: the 80% cap applies to the homestead regardless of loan type. The calculator does not automatically enforce the 12-month seasoning rule or the 2% fee cap — confirm with your lender.
Refinance Cost Calculator
The cost calculator provides an itemized estimate of your total refinance closing costs.
Cost Components and Defaults
| Cost Item | Default Estimate | Basis |
|---|---|---|
| Origination fee | 1.0% of loan amount | CFPB Loan Estimate guidance; national average range 0.5%–1.5% |
| Appraisal | $550 | National average per CFPB consumer data; range $400–$700 |
| Title search & insurance | $1,500 | American Land Title Association average; range $1,000–$2,500 |
| Recording fees | $200 | National midpoint; range $50–$500 depending on county |
| Underwriting fee | $650 | Lender-average; range $400–$900 |
| Prepaid interest | Calculated from inputs | Days remaining in month × daily rate × new balance |
All defaults are adjustable. We strongly recommend entering your lender's actual Loan Estimate figures for precise results. The 2% rule-of-thumb total we use in other calculators is an approximation — your actual costs can range from under 1% (no-closing-cost refi) to over 3% in high-cost states like New York.
FHA Refinance Calculator
The FHA refinance calculator compares an FHA Streamline refinance against switching to a conventional loan — including MIP cost, monthly savings, and net tangible benefit check.
FHA Mortgage Insurance Premium (MIP) Rates
Annual MIP is charged monthly and depends on loan term, LTV, and loan amount. The most common tier used for 30-year loans at or below the conforming limit:
| Term | Base Loan Amount | LTV | Annual MIP |
|---|---|---|---|
| 30 yr | ≤ $726,200 | ≤ 90% | 0.50% |
| 30 yr | ≤ $726,200 | > 90% | 0.55% |
| 30 yr | > $726,200 | ≤ 90% | 0.70% |
| 30 yr | > $726,200 | > 90% | 0.75% |
| 15 yr | ≤ $726,200 | ≤ 90% | 0.15% |
| 15 yr | ≤ $726,200 | > 90% | 0.40% |
Source: HUD Mortgagee Letter 2023-05
Upfront MIP (UFMIP)
(Typically financed into the new loan balance)
FHA Streamline Net Tangible Benefit
HUD requires a "net tangible benefit" for FHA Streamline refinances. The calculator checks the standard fixed-to-fixed test:
Net Tangible Benefit = Current Combined Rate − New Combined Rate ≥ 0.50%
FHA to Conventional
When LTV is at or below 80%, the calculator also models switching to a conventional loan where no PMI or MIP applies. The comparison shows: new conventional payment vs. new FHA payment (with MIP), break-even on the difference, and total interest cost over the remaining term.
Key assumptions:
• MIP rates use HUD's 2023 revised schedule (effective March 20, 2023). Rates are subject to change by HUD mortgagee letter.
• UFMIP is assumed to be financed into the loan. If paid at closing, subtract it from the new loan balance.
• FHA MIP is charged for the full loan term for LTV > 90% on 30-year loans; for loans at or below 90% LTV, MIP drops off at 11 years.
VA Refinance (IRRRL) Calculator
The VA refinance calculator models an Interest Rate Reduction Refinance Loan (IRRRL) — the VA's streamline refinance — showing monthly savings, funding fee cost, and whether the loan meets the VA's net tangible benefit test.
VA Funding Fee — IRRRL
| Borrower Status | Funding Fee |
|---|---|
| Standard (all loan uses) | 0.50% of loan amount |
| Disability-exempt | 0% (exempt) |
Source: VA Funding Fee Table (38 U.S.C. § 3729)
VA Net Tangible Benefit Test (IRRRL)
For a fixed-to-fixed IRRRL, VA requires the new interest rate to be at least 0.50% lower than the existing rate. The calculator checks this automatically and displays a pass/fail result. Additional lender overlays may require recoupment of fees within 36 months:
Pass if Recoupment Months ≤ 36
Funding Fee Financing
Financed Funding Fee = Current Balance × 0.005 (if not exempt)
Key assumptions:
• The calculator assumes a fixed-to-fixed IRRRL. ARM-to-fixed and cash-out VA refinances use different funding fee rates and rules.
• Disability exemption eligibility must be confirmed with the VA — the calculator cannot verify your status.
• IRRRL does not require a VA appraisal or new Certificate of Eligibility. No-appraisal assumption is baked into the closing cost defaults.
Mortgage Points Calculator
The mortgage points calculator determines whether paying discount points to buy down your interest rate saves money over your expected ownership period.
What One Point Costs
Example: 1 point on a $400,000 loan = $4,000
Rate Reduction per Point
The actual rate reduction per point varies by lender, market conditions, and loan type. The calculator uses a default of 0.25% per point — a commonly cited midpoint of the typical 0.125%–0.375% range. You can override this with your lender's actual quote.
Break-Even Formula
Payment (with points) = amortization formula at (stated rate − rate reduction)
Monthly Savings = Payment (no points) − Payment (with points)
Points Cost = Number of Points × (Loan Amount × 0.01)
Break-Even Months = Points Cost ÷ Monthly Savings
Long-Term Savings
Total Interest (with points) = sum of interest over full term at reduced rate
Net Lifetime Savings = (Total Interest no points − Total Interest with points) − Points Cost
Key assumptions:
• Break-even ignores the time value of money (upfront cash vs. future savings). Discounting at a 4%–6% opportunity cost rate would extend the effective break-even by several months.
• The calculation assumes you keep the loan for the full break-even period and beyond. If you refinance or sell before break-even, you lose money on the points.
• Discount points are generally tax-deductible in the year paid (for a home purchase) or ratably over the loan term (for a refinance). See IRS Publication 936.
ARM vs Fixed Calculator
The ARM vs Fixed calculator compares total cost over your expected stay between an adjustable-rate mortgage and a fixed-rate mortgage, using three ARM scenarios: projected, flat, and worst-case.
ARM Structure
A hybrid ARM (e.g., 5/1 ARM) charges a fixed rate for an initial period, then adjusts annually based on an index plus a margin. Standard adjustment caps limit rate movement:
| Cap Type | Typical Value | Effect |
|---|---|---|
| Initial adjustment cap | 2% | Max change at first adjustment after fixed period |
| Periodic adjustment cap | 2% | Max change at each subsequent annual adjustment |
| Lifetime cap | 5% above initial rate | Maximum rate over the life of the loan |
Three Scenarios
Flat: ARM rate stays at the initial teaser rate for the full period
Worst-Case: ARM hits the per-adjustment cap (up) every year until lifetime cap
Month-by-Month Simulation
For each ARM scenario the calculator runs a full amortization month by month. At each annual adjustment boundary, the rate changes, and the monthly payment is recalculated from the remaining balance at the new rate for the remaining term. This is the correct method — not a flat-rate shortcut.
Comparison Output
The calculator computes total interest paid from month 1 to your expected stay date for both the fixed loan and each ARM scenario. The stay date may fall before the full term, in which case the comparison uses the remaining balance at that month as the "payoff" and total interest paid to that point.
Key assumptions:
• ARM index and margin are not separately modeled — you enter the projected future rate directly.
• The worst-case scenario assumes the rate rises by the per-adjustment cap at every adjustment without limit (other than the lifetime cap). This models maximum payment shock.
• Closing costs for the new loan are included in the total cost comparison if entered. Prepayment penalties on the existing ARM are not modeled.
APR Calculator
The APR calculator computes the Annual Percentage Rate for two loan offers simultaneously — factoring in lender fees — so you can identify the cheaper loan on an apples-to-apples basis.
What APR Measures
APR (Annual Percentage Rate) is the effective annual cost of the loan, including the stated interest rate plus certain lender fees (origination, points, broker fees). It is the rate that makes the present value of all your scheduled payments equal the net loan proceeds (loan amount minus upfront fees). APR disclosure is required under the Truth in Lending Act (TILA) and Regulation Z.
Calculation Method — Bisection / IRR
There is no closed-form algebraic solution for APR given fees, because fees effectively change the loan balance. We use the standard bisection method to solve the implicit equation numerically (100 iterations; precision is better than 0.0001%):
Net Proceeds = Loan Amount − Upfront Fees
Find effective monthly rate r such that:
Net Proceeds = M × [1 − (1 + r)−n] ÷ r
APR = r × 12 × 100 (annualized, expressed as %)
Search bounds: r ∈ [0.0001/12, 2.0/12] (i.e., 0.01% to 200% annual)
Why APR > Stated Rate
When a lender charges upfront fees, you receive less than the face loan amount but make payments as if you received the full amount. Your effective cost is therefore higher than the stated rate. A loan with a lower stated rate but high fees can have a higher APR than a loan with a higher stated rate and no fees.
APR Comparison Logic
APR Difference = |APR_A − APR_B|
Monthly Payment Difference = |M_A − M_B|
Total Cost = (M × n) + Upfront Fees (paid at closing)
Key assumptions:
• APR assumes you hold the loan for the full term. For short holds, a lower-fee loan with a higher rate may actually be cheaper — the calculator shows monthly payment and total cost to help you evaluate this.
• Only upfront lender fees are included. Monthly fees (servicing charges, etc.) are not standard and not modeled.
• TILA-calculated APR uses a specific fee-inclusion rule (not all fees are required to be included). Our calculator lets you enter only the fees you choose to compare — it does not independently determine what TILA requires to be in the APR disclosure.
No-Closing-Cost Refinance Calculator
The no-closing-cost refinance calculator compares three ways to handle closing costs and identifies which strategy costs least over your planned hold period.
Three Options Compared
| Option | Upfront Cash | Loan Balance | Interest Rate |
|---|---|---|---|
| A — Pay Upfront | Full closing costs | Original balance | Quoted rate |
| B — Roll Into Balance | $0 | Original balance + closing costs | Quoted rate |
| C — Lender Credit | $0 | Original balance | Higher rate (lender pays fees) |
Calculation Method
For each option the calculator runs a full month-by-month amortization schedule for your expected hold period. At the end of the hold period, the remaining balance is treated as a payoff (sale or re-refinance). Only the interest accrued during your hold period is included — not interest on unpaid principal beyond your stay.
For each month m = 1 … min(holdMonths, term×12):
interest(m) = balance(m−1) × (rate ÷ 12 ÷ 100)
balance(m) = balance(m−1) − (M − interest(m))
Return sum of interest(1 … holdMonths)
Option A total cost = upfront costs + totalInterest(balance, rate, term, holdMonths)
Option B total cost = totalInterest(balance + costs, rate, term, holdMonths)
Option C total cost = totalInterest(balance, lcRate, term, holdMonths)
Winner Selection
Lender Credit Rate (Option C)
Option C requires a second rate input — the higher rate your lender quotes when they agree to cover all closing costs. Typically this premium is 0.25%–0.375% above the par rate. If you leave this input blank or enter 0, Option C is hidden and the calculator compares only A vs B.
Key assumptions:
• All three options use the same loan term. Only the balance, upfront cash, and rate differ.
• The hold period is your expected time before selling or refinancing again. For a permanent hold, use 30 years.
• Rolling costs into the balance (Option B) uses the same interest rate as paying upfront — no rate premium is assumed. If your lender quotes a higher rate for the larger balance, model that as Option C instead.
• Time value of money is not applied. If the upfront cash would otherwise earn a meaningful return (e.g., invested at 5%+), the true break-even for paying upfront is longer than the raw comparison shows.
Refinance Payment Calculator
The Refinance Payment Calculator applies the standard fixed-rate amortization formula to compute the new monthly principal-and-interest payment after refinancing, plus an amortization milestone table.
Monthly Payment
Given loan balance P, annual rate ra, and term of n years:
r = ra / 100 / 12
n_months = n × 12
M = P × r × (1+r)^n_months / ((1+r)^n_months − 1)When rate = 0, the payment is P ÷ n_months (no interest, principal divided equally).
Amortization Milestones
For each month m from 1 to n_months:
interest_m = balance_(m-1) × r
principal_m = M − interest_m
balance_m = balance_(m-1) − principal_mThe milestone table captures remaining balance, cumulative interest paid, and % of original principal repaid at years 5, 10, 15, 20, 25, and payoff.
Key Assumptions
Key assumptions:
• Payments are monthly with no prepayment.
• The formula computes P&I only — taxes, insurance, and PMI are excluded.
• The optional "current monthly P&I" comparison uses the user-entered value; this calculator does not derive a current payment from a prior balance or rate.
HELOC vs Cash-Out Refinance Calculator
The HELOC vs Cash-Out Refinance Calculator computes and compares the total financing cost of each option over a user-defined hold period.
Cash-Out Refinance Total Cost
The new balance is existing balance + cash drawn. Monthly payment Mrefi is computed with the standard amortization formula above. We sum interest paid month-by-month up to the hold period, then add upfront closing costs:
refi_int = Σ interest(month 1 → hold_months) on (curBal + cashNeeded) at refiRate / refiTerm
refi_total_cost = closingCosts + refi_intHELOC Total Cost
The first mortgage is kept intact. Its interest contribution over the hold period is computed identically to the amortization loop above (on curBal, curRate, curTerm). The HELOC is modeled in two phases:
- Draw period (interest-only): monthly interest = cashNeeded × helocRate / 100 / 12, accumulated for min(drawMonths, holdMonths).
- Repayment period (amortizing): Mheloc = calcPayment(cashNeeded, helocRate, repayYears), accumulated month-by-month for the remaining hold period after the draw phase ends.
heloc_total_cost = mortgage_interest(hold) + draw_interest(hold) + repay_interest(hold)Winner Selection
The option with the lower total cost over the hold period is declared the winner. The verdict message states the dollar difference.
Key Assumptions
Key assumptions:
• The HELOC is modeled as fully drawn at closing — partial draws produce lower HELOC interest costs and would favor the HELOC more strongly.
• The HELOC rate is treated as fixed at the input value. Actual HELOCs are typically variable; rate increases would raise HELOC costs.
• No prepayment of either loan during the hold period is modeled.
• Combined HELOC monthly payments shown are: first-mortgage P&I + HELOC interest-only (draw phase) and first-mortgage P&I + HELOC amortizing payment (repayment phase).
• Taxes, insurance, and PMI are excluded from both options.
Data Sources for Default Values
Default values in our calculators are set from published research, not invented estimates:
| Data Point | Source |
|---|---|
| Average closing cost range (1.5%–3%) | CFPB Closing Disclosure research |
| Appraisal cost range ($400–$700) | CFPB consumer complaint data and Freddie Mac servicer surveys |
| Title insurance range ($1,000–$2,500) | American Land Title Association (ALTA) annual survey |
| PMI cancellation thresholds | CFPB — Homeowners Protection Act |
| Max LTV thresholds | Fannie Mae Selling Guide, Freddie Mac Selling Guide, HUD Handbook 4000.1, VA Lenders Handbook |
| Conforming loan limits | FHFA Annual Conforming Loan Limit Data |
| FHA MIP rates | HUD Mortgagee Letter 2023-05 (effective March 20, 2023) |
| VA IRRRL funding fee (0.50%) | VA Funding Fee Table — 38 U.S.C. § 3729 |
| APR calculation method | Truth in Lending Act (TILA), 15 U.S.C. § 1606; CFPB Regulation Z, 12 C.F.R. § 1026.22 |
| Discount points typical rate reduction | CFPB consumer guide; Freddie Mac Primary Mortgage Market Survey historical data |
For a full list of sources used in our editorial content, see our Sources & References page.
What Our Calculators Do Not Include
- ARM index/margin modeling: The ARM vs Fixed calculator lets you model ARM scenarios using a projected future rate, but it does not independently track the underlying index (SOFR, CMT) or margin — you enter the projected rate directly. Future index movements cannot be predicted.
- Tax implications: Mortgage interest deductibility, points deductibility, and cash-out tax treatment are not modeled. See IRS Publication 936.
- Escrow and impounds: Property taxes, homeowners insurance, and flood insurance are not included in payment estimates.
- Credit score adjustments: Lenders add rate adjustments (LLPAs) based on credit score and LTV. Our calculations use the rate you enter without modeling how your score affects the available rate.
- Lender-specific fees: Some lenders charge application fees, rate-lock fees, or courier fees not captured in our defaults.
- Time value of money: Break-even and savings comparisons are nominal, not discounted. A full NPV analysis would discount future savings at your opportunity cost rate.
For a complete and binding cost estimate, request an official Loan Estimate from your lender. Lenders are required by TRID (CFPB regulation) to provide this within 3 business days of receiving your application.
Analysis Tools — Calculation Methodology
The nine Analysis Tools use multi-factor scoring and projection models rather than single-formula outputs. Each is documented below.
1. Refinance Analyzer
Produces a Risk Score (0–100) and a Confidence Score (0–100) from six weighted inputs.
Monthly savings: CurrentPayment − NewPayment. Break-even: ClosingCosts ÷ MonthlySavings. Equity projections use standard amortization at the new rate over the remaining term.
2. Mortgage Health Score
Assigns a letter grade (A–F) from a 100-point scale across four dimensions plus adjustments.
3. Refinance Timing Analyzer
Scores the timeliness of refinancing on a 0–100 Timing Score from five factors.
4. Mortgage Cost Timeline
Projects year-by-year amortization for up to two loans using the standard amortization formula.
5. Cash-Out Scenario Planner
Models three cash-out use-case scenarios plus an opportunity cost table.
6. State Cost Analyzer
Looks up closing cost components for all 50 states from a built-in data table and computes total estimated closing cost.
7. Mortgage Strategy Simulator
Compares five parallel strategies over a user-defined horizon using standard amortization and future-value formulas.
8. Refinance Readiness Assessment
Seven-question quiz producing a Readiness Score (0–100) and tier classification.
9. Mortgage Scenario Lab
Free-form comparison of up to four parallel mortgage scenarios.
Last Reviewed
This methodology page was last reviewed and updated: July 2026 (added Analysis Tools documentation: Refinance Analyzer, Mortgage Health Score, Timing Analyzer, Cost Timeline, Cash-Out Scenario Planner, State Cost Analyzer, Strategy Simulator, Readiness Assessment, and Scenario Lab).
Calculator formulas are mathematically static (they implement published mortgage finance standards that do not change). Default values are reviewed annually or when a relevant agency updates published guidance.
Questions about our methodology? Contact us or see our Editorial Policy.