Free Mortgage Calculator: Monthly Payment, Total Interest, Early Payoff
Calculate your monthly mortgage payment and total interest with the standard fixed-rate amortization formula. Run extra-payment scenarios to see how many years and dollars you save. 100% client-side — loan figures never leave your browser.
Standard Amortization Formula
Real fixed-rate mortgage math (M = P·r·(1+r)ⁿ / ((1+r)ⁿ−1)) — not a back-of-envelope approximation. Handles zero-interest edge case correctly.
Extra-Payment Scenarios
Add an optional extra monthly principal payment. We re-amortize month-by-month and tell you exactly how many years AND dollars in interest you save.
Year-by-Year Summary
See principal paid, interest paid, and ending balance for every year of the loan — perfect for spotting when the equity scale tips from interest-heavy to principal-heavy.
100% Client-Side
Loan amount, interest rate, and your full amortization schedule stay entirely in your browser. No upload, no save, no analytics.
The Mortgage Calculator That Treats You Like an Informed Adult
Mortgage calculators are everywhere; useful ones are rare. The standard formula gives the monthly payment in one line of arithmetic — but the questions that actually matter (how much interest am I paying, can I shave years off with an extra $100 a month, when does the principal-vs-interest split flip?) need a full amortization simulation. Our Free Online Mortgage Calculator runs that simulation in your browser, shows year-by-year balance, and computes the savings of any extra-payment scenario you want to try.
Pair this calculator with our Tip Calculator (everyday financial math), the Age Calculator (retirement-date projections work the same way), and the BMI Calculator (sibling general-utility tool with a health screening focus).
The Amortization Formula, Decoded
P · r · (1 + r)ⁿ
M = ─────────────────────
(1 + r)ⁿ − 1- M — monthly principal-plus-interest payment
- P — principal (loan amount remaining)
- r — monthly interest rate (annual rate ÷ 12 ÷ 100)
- n — total number of monthly payments (term in years × 12)
One formula. Two hundred years old (Augustin Cournot, 1838). Used by every fixed-rate lender on Earth. The zero-interest special case degenerates to M = P / n; we handle that branch explicitly so a 0% mortgage simulation doesn't divide by zero.
US 30-Year Fixed Mortgage Rates: Historical Context
| Decade | Average Rate | Context |
|---|---|---|
| 1971–1980 | 8.9% | 1970s stagflation |
| 1981–1990 | 12.7% | Volcker rate-hike era; peaked at 18.4% in Oct 1981 |
| 1991–2000 | 7.9% | Greenspan post-recession easing |
| 2001–2010 | 6.0% | Housing boom + Great Recession trough |
| 2011–2020 | 4.0% | Post-GFC ultra-low rates |
| 2021–2025 | 5.9% | Inflation-driven Fed tightening |
Source: Freddie Mac Primary Mortgage Market Survey. Decade averages calculated from annual averages. Today's rate may be lower or higher than recent history; always get a written rate quote.
Why Extra Payments Are Mathematically Magical
The compounding mechanism that grows your debt at the bank also works in reverse when you pay it down faster. Three principles to internalise:
1. Early Payments Hit Hardest
An extra $100 in month 1 of a 30-year mortgage saves about $440 in interest over the life of the loan. The same $100 in month 300 saves about $10. Front-loaded extra payments are 40× more powerful than late ones.
2. Even Small Amounts Compound
$50 extra per month on a $300,000 / 6.5% / 30-year mortgage saves about $40,000 in interest and ~3 years — from a 0.6% increase in the monthly payment.
3. One Extra Payment Per Year
Sending a 13th payment each year (equivalent to one extra month divided across 12) typically shaves 4–5 years off a 30-year mortgage. Annual tax refund or bonus is a natural source.
4. Beware Prepayment Penalties
Some loans (rare in the US since 2014 Dodd-Frank rules; more common abroad) charge a fee for early payoff. Always confirm before accelerating — ask for the loan's prepayment clause in writing.
When NOT to Pay Extra on Your Mortgage
1. No Emergency Fund Yet
Pay yourself first. A 3–6 month emergency fund stops a job loss or medical bill from forcing a foreclosure. Liquidity beats equity in a crisis.
2. Higher-Interest Debt
Credit card at 22% or a personal loan at 12% should be paid before a mortgage at 6%. Always attack the highest rate first.
3. Employer 401(k) Match
A 50% or 100% employer match on retirement contributions is an immediate 50–100% return. Capture that before paying mortgage extra.
4. Low-Rate Mortgages
If you locked a 3% mortgage in 2021, the math favours putting extra money in index funds (long-term ~7% real return) over paying down the 3% debt.