About Mortgage Calculator

Monthly payment + total interest for any loan amount, rate, term. Part of the DevTools Surf developer suite. Browse more tools in the Calculators collection.

Use Cases

• Compare monthly payments across different rates
• Estimate affordability before applying for a loan
• Project total interest paid over the loan term
• Model the impact of extra principal payments on the payoff date

Tips

• Rate is entered as APR (e.g. 6.5 for 6.5%)
• Term is in years; most US mortgages are 30 or 15
• Total interest can exceed the principal on 30-year loans

Fun Facts

• The modern 30-year fixed mortgage was invented by the US federal government via the HOLC in 1933 — before then, most mortgages were 5-year balloon loans.
• In Japan, some banks offer 100-year mortgages that can be passed down through generations — the longest mortgage terms in the world.
• The amortization formula used by every mortgage calculator was developed by actuaries in the 18th century and hasn't changed since — it's one of the oldest financial formulas still in daily use.

FAQ

Does it include property tax and insurance?

Toggle for PITI (Principal + Interest + Taxes + Insurance). Without these, the monthly payment looks artificially low.

PMI — when?

Private Mortgage Insurance is required on conventional loans with <20% down payment. Toggle to include in monthly cost. Typically drops off at 22% equity.

Fixed or adjustable rate?

Fixed by default. For ARM (adjustable), pick the initial rate + adjustment schedule. Shows payment over time as rate changes.

Total interest paid?

Yes — shown prominently. On a 30-year mortgage, total interest often matches or exceeds the principal. Important perspective when comparing loan terms.