onlinecalculator.me

Free online mortgage calculator

A mortgage is a long-term loan you use to buy a home. This calculator shows the monthly payment, total interest, and when you'll pay off the balance.

Mode
We assumed —
We assumed —
We assumed —
Monthly payment
—
Principal + interest
Total interest
—
Over the full term
Total paid (P+I)
—
Principal repaid plus all interest
About this calculator

How to use

  1. Enter the loan amount, interest rate (APR), and term in years. Light mode is enough for a quick estimate.
  2. Optionally, add an extra monthly payment to see how much interest and time it saves.
  3. Switch to Extended mode to include property tax, homeowners insurance, HOA dues, or PMI. The monthly total updates to reflect everything lumped together.
  4. Use “Show schedule” to see each month’s interest, principal, and remaining balance.
  5. Press “Share” to copy a link with your inputs. Save as PDF for a clean printout, or Save as image for a quick screenshot.

The formula

The fixed-rate monthly payment is the classic annuity formula:

      P · r · (1 + r)^n
M  =  ─────────────────
        (1 + r)^n − 1

Where:

  • P is the loan principal (amount borrowed).
  • r is the monthly rate — the annual APR divided by 12, as a decimal. A 6.5% APR becomes r = 0.065 / 12 ≈ 0.005417.
  • n is the total number of monthly payments (term in years × 12).
  • If r = 0, the formula collapses to M = P / n.

Each month, the interest portion is balance × r, and the principal portion is M − interest. The balance drops, next month’s interest is smaller, and the principal portion grows — that’s the amortization.

Worked example

Borrow $300,000 at 6.5% APR for 30 years.

  • P = 300,000
  • r = 0.065 / 12 ≈ 0.00541667
  • n = 360
  • (1 + r)^n ≈ 7.04724
  • Numerator: 300,000 × 0.00541667 × 7.04724 ≈ 11,451.71
  • Denominator: 7.04724 − 1 = 6.04724
  • M ≈ 11,451.71 / 6.04724 ≈ 1,896.20

So the monthly principal-and-interest payment is about $1,896.20. Over 360 months, you pay roughly $682,632 total, of which $382,632 is interest.

Add $200 of extra principal every month and the same loan pays off about 5.5 years early, saving around $85,000 in interest. Try it in the calculator above.

Notes

  • The calculator uses monthly compounding, which is what US mortgages do. Some countries compound differently — the formula still applies, but with their conventions.
  • Property tax, insurance, HOA, and PMI are estimates. Your actual escrow may be rebalanced yearly by your lender.
  • This tool is for planning, not a lending decision. Compare any official Loan Estimate you receive against the numbers here.

Frequently asked

How is the monthly mortgage payment calculated?
For a fixed-rate loan, the formula is M = P · r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the principal, r is the monthly rate (annual APR ÷ 12), and n is the total number of monthly payments. If the rate is zero, it reduces to M = P / n.
Does this calculator include property tax and insurance?
Only in extended mode. Light mode shows just principal and interest; extended mode adds property tax, homeowners insurance, HOA, and PMI. The amortization schedule always reflects principal and interest plus any extra payment.
How do extra monthly payments change the loan?
Extra payments go straight to principal, which cuts total interest and shortens the payoff. The monthly scheduled payment stays the same — only the balance drops faster. You can see the effect in the Total interest and payoff time next to the result cards.
Is the amortization schedule exact?
It uses standard monthly compounding with rounded dollar amounts per period. The last payment is trimmed so the final balance is exactly zero. For escrow items (tax, insurance, HOA, PMI) we spread the annual figure evenly across months, which matches how most lenders quote the escrowed total.
Can I share a calculation with someone?
Yes. Press the Share button and a link with your inputs encoded in the URL is copied to your clipboard. Opening it reloads the same numbers, including extended fields if you used them.