Mortgage Calculator: Monthly Payment & Total Interest
Work out what a fixed-rate mortgage will actually cost you each month, and how much of the total goes to interest over the life of the loan.
Adjust the inputs and select Calculate for a full breakdown.
Year-by-year amortization schedule
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Monthly payment | Total interest | Total of payments |
|---|---|---|---|
| $300k · 6.5% · 30-year | $1,896.20 | $382,633.47 | $682,633.47 |
| $300k · 6.5% · 15-year | $2,613.32 | $170,397.98 | $470,397.98 |
| $450k · 7.0% · 30-year | $2,993.86 | $627,790.04 | $1,077,790.04 |
| $250k · 5.5% · 20-year | $1,719.72 | $162,732.38 | $412,732.38 |
How This Calculator Works
The calculator takes your loan amount, annual interest rate, and term, then applies the fixed-rate amortization formula to find the constant monthly payment that fully repays the loan. It converts your APR to a monthly rate and the term to a number of monthly payments, then derives the payment and rebuilds the schedule month by month so you can see how principal and interest shift over time.
The Formula
Fixed-Rate Amortization
P = loan amount, r = monthly rate (APR ÷ 12), n = number of monthly payments
Worked Example
Take a $300,000 loan at 6.5% APR over 30 years. The monthly rate is 0.5417% and there are 360 payments, giving a monthly figure of about $1,896. Over the full term you repay roughly $682,600 — meaning interest alone is about $382,600, larger than the amount you originally borrowed.
Key Insight
On a 30-year mortgage, the early years are almost entirely interest. Even a small extra payment in year one removes far more lifetime interest than the same payment in year fifteen.
PITI — the full monthly payment, not just principal + interest
Most mortgage calculators (including this one) show 'P&I' — principal + interest. The actual monthly payment is usually PITI: Principal + Interest + Property Taxes + Homeowners Insurance. PITI is what your bank actually debits monthly, what mortgage lenders use to qualify you, and what determines your true housing cost.
Concrete example: $400,000 mortgage at 7% over 30 years = P&I of $2,661/month. But add property tax of $6,000/year ($500/month) + homeowners insurance of $1,800/year ($150/month) + (if down payment under 20%) PMI of $200-400/month + (if HOA) $200-500/month. Total real PITI: roughly $3,500-3,800/month — 30-40% more than P&I alone.
Lenders qualify you on full PITI plus monthly debts. The classic rule: PITI should not exceed 28% of gross monthly income (housing ratio), and total debts (PITI + cars + cards + student loans) shouldn't exceed 36% (total debt-to-income ratio). With current rates, the 28% rule typically caps qualifying loan amount at 3-4× annual income — much less than buyers think they can afford.
The amortization curve: why early years are all interest
Mortgages amortize on a fixed schedule that front-loads interest. On a 30-year $400k mortgage at 7%, the FIRST monthly payment of $2,661 splits as $2,333 interest + $328 principal — meaning only 12% of your first payment actually reduces the loan. By year 10, the split shifts to ~$1,775 interest + $886 principal. By year 20, it's $1,016 interest + $1,645 principal. By year 30, the final payment is almost entirely principal.
Practical implication: making extra principal payments in early years saves enormous interest. An extra $200/month from year 1 saves about $80,000 over the loan's life on a $400k/7%/30yr loan AND shortens the loan by ~5 years. The same $200/month started in year 15 saves only ~$15,000. Time-value asymmetry favors early extra payments.
Refinancing math: refinancing 'restarts' the amortization clock. Refinancing $300k remaining balance from 7% to 5% (years 1-15 saved by lower rate) but extending term back to 30 years can paradoxically INCREASE total interest paid if you're not careful. The right refinance shortens the remaining term OR maintains it — never extend.
The 'true cost' over 30 years: principal + interest + opportunity
On a $400,000 mortgage at 7% over 30 years, total payments = $2,661 × 360 = $957,960. That's $557,960 of interest on top of the $400,000 borrowed. Interest is roughly 1.4× the original loan amount at current rates — a stark number that's rarely shown.
Add: down payment ($80,000 at 20%), closing costs ($8,000-15,000), maintenance (typically 1-3% of home value/year × 30 years = $120k-360k on a $400k home), property taxes ($180,000+ over 30 years), insurance ($54,000+), inflation-adjusted lost opportunity on the down payment if invested elsewhere. The TRUE 30-year cost of owning a $400k home: easily $1.5M-$2M.
This is not an argument against owning — for most families, owning still beats renting over a 30-year horizon AND builds equity. But understand: a mortgage is the largest cash flow commitment of most lives. The monthly payment is just the visible tip; the total commitment is roughly 4-5× the home's purchase price over its lifetime.
Monthly P&I payment by rate and loan amount (30-year fixed)
Principal + interest only. Add property tax, insurance, PMI (if applicable), and HOA fees for true monthly housing cost (PITI).
| Loan amount | 5% rate | 6% rate | 7% rate | 8% rate |
|---|---|---|---|---|
| $200,000 | $1,074 | $1,199 | $1,331 | $1,468 |
| $300,000 | $1,610 | $1,799 | $1,996 | $2,201 |
| $400,000 | $2,147 | $2,398 | $2,661 | $2,935 |
| $500,000 | $2,684 | $2,998 | $3,327 | $3,669 |
| $750,000 | $4,026 | $4,496 | $4,990 | $5,503 |
| $1,000,000 | $5,368 | $5,996 | $6,653 | $7,338 |
30-year fixed. For 15-year: payment ~1.6× higher monthly but ~40% less total interest. For ARM rates, payment is initial only — varies after the fixed period. Add ~30-40% to monthly figures for total PITI (taxes + insurance + PMI + HOA).
Frequently Asked Questions
Does this calculator include property taxes and insurance?
No. This figure is principal and interest only. Add escrow for property taxes, homeowners insurance, and any PMI separately to get your full monthly housing cost.
What interest rate should I enter?
Enter the APR your lender quoted. If you are still shopping, use the average rate for your credit tier and loan term as a planning estimate, then refine it once you have a real quote.
How does the loan term change the payment?
A longer term lowers the monthly payment but raises total interest paid, because you are borrowing the money for longer. A shorter term does the reverse.
Should I choose a 15-year or a 30-year mortgage?
A 15-year mortgage carries a higher monthly payment but cuts total interest dramatically because the balance is repaid in half the time. A 30-year keeps payments affordable but costs far more interest overall. Compare both in the scenario table above before deciding.
How much does a small rate change affect the payment?
On a large balance the effect is significant. Even a half-point difference in APR can change the monthly payment by tens of dollars and the lifetime interest by tens of thousands, which is why shopping multiple lenders is worth the effort.
Does making extra principal payments help?
Yes, substantially. Any payment above the scheduled amount goes straight to principal, which shrinks the balance that future interest is charged on and shortens the loan. The earlier in the schedule you do it, the larger the lifetime saving.
References & Authoritative Sources
- CFPB — Consumer Financial Protection Bureau — Mortgage payment calculator and home affordability guide · consulted May 31, 2026 · Federal consumer protection — qualifying ratios, PITI definition, total housing cost guidance
- Freddie Mac — Primary Mortgage Market Survey — weekly mortgage rates · consulted May 31, 2026 · Authoritative source for current US mortgage rates
- Federal Reserve Board — Regulation Z — Truth in Lending Act — mortgage disclosures · consulted May 31, 2026 · Statutory basis for APR disclosure, Good Faith Estimate, and Closing Disclosure
Related Calculators
Data Sources & Benchmarks
This calculator draws on 3 independent, dated sources. The starting values for loan amount and interest rate are taken from the benchmarks below and refresh whenever the snapshots are updated.
Methodology & Review
Payments use the standard fixed-rate amortization formula. Figures cover principal and interest only; escrow items such as property tax, homeowners insurance, and PMI are excluded by design. Results are reviewed against published lender amortization tables.
Updated