Mortgage Calculator
Type a home price and rate. See the monthly payment, total interest, and when you'll own the place outright. Add property tax, insurance, HOA, or an extra principal payment to see the true cost — and how a few hundred extra dollars a month compounds into years off your loan.
Amortization schedule
| # | Payment | Principal | Interest | Balance |
|---|
What this calculator answers
- "What's my monthly payment?" — full PITI + HOA breakdown, not just principal & interest.
- "How much interest will I pay total?" — over the entire amortisation, including extra payments.
- "When do I pay it off?" — exact payoff month, useful when you're throwing extra principal at the loan.
- "What does $200 extra a month actually save me?" — change one input, see total interest drop by tens of thousands.
The numbers that move the payment most
Three inputs swamp everything else on a fixed-rate mortgage:
- Loan amount — price minus down payment. The payment is roughly linear in this; doubling the loan doubles the P&I.
- Interest rate — small differences compound. On a $400K, 30-year loan, a 6.5% vs 7.0% rate is ~$135/month and ~$48,000 total interest.
- Term — 15 vs 30 years roughly halves the total interest but raises the monthly by ~50%.
Property tax, insurance, and HOA are real money but rarely move the deal — they're additive, not multiplicative. The first three drive whether the house is affordable.
Why client-side
Big-bank mortgage calculators are mostly an excuse to capture your email and sell you to a loan officer. The math is the same on every site. Doing it in your browser means no email gate, no rate-shopping spam, and no leak of "user X is shopping for a $750K home in zip 94110" to whoever buys the data.
tooljo's calculator runs ~5 KB of JavaScript. The URL hash is
your save state — bookmark a scenario, share it with a partner, paste it
into a notebook to compare options.
Tips
- Compare two scenarios by opening the page in two tabs with different inputs. The URL hash makes each tab self-describing.
- Use the % field to flip between dollar and percentage down. Linked two-way — change one and the other updates.
- Test the "extra principal" lever. On a 30-year loan, $200/month extra typically shaves 5–7 years and tens of thousands in interest. The number is usually larger than people expect.
- Don't forget closing costs — this calculator covers the loan itself, not the 2–5% in fees you pay at closing. Budget those separately.
PMI and biweekly payments, done honestly
- PMI — set a down payment under 20% and a PMI field appears. The monthly cost is added to the payment and the schedule simulation shows exactly when your balance hits 80% of the price (the point PMI can drop off) and what it costs in total until then.
- Biweekly payoff — the checkbox runs a true every-2-weeks simulation (26 half-payments = 13 full payments a year) and reports how much sooner you finish and the interest saved versus monthly payments.
- Amortization schedule — expand it to see every month's principal, interest, and balance, or download the whole thing as CSV.
What this calculator does not do
- ARMs and balloon loans — fixed rate for the whole term only.
- Tax deduction — varies by jurisdiction and standard-deduction choice. This is a payment calculator, not a tax planner.
FAQ
Is anything I enter sent to a server?
No. Every number you type stays in your browser — open DevTools → Network and verify. The URL hash carries your inputs so you can share a link, but that hash is only sent to your own browser.
How is the monthly payment calculated?
Standard PMT formula:M = P × [r(1+r)n] / [(1+r)n − 1]
where P is the loan amount (price minus down payment), r is the monthly interest rate (APR ÷ 12), and n is the number of monthly payments (years × 12).
Does this include property tax, insurance, and HOA?
If you fill those fields in (under "Add property tax, insurance, HOA"), yes — they're added to the monthly total to give you a true PITI + HOA figure. Property tax and insurance are entered annually and divided by 12 internally; HOA is monthly.
What about extra principal payments?
Enter an amount in "Extra principal / month" and the calculator amortises the loan with that extra payment applied each month. The "Total interest" and "Payoff in" outputs reflect the savings — typically dramatic on a 30-year loan.
What is PMI, and when does it drop off?
Private mortgage insurance protects the lender when you put less than 20% down — you pay it, typically 0.3–1.5% of the loan per year, folded into the monthly payment. Put a down payment under 20% into the calculator and a PMI field appears (default 0.8%/yr). By federal law PMI must be cancelled automatically once the balance amortises to 78% of the original value, and you can request cancellation at 80% — the calculator simulates your schedule and shows the month your balance reaches 80%, plus roughly what PMI costs you in total until then. Extra principal payments pull that date forward.
Do biweekly payments really pay the loan off faster?
Yes — but not because of the frequency itself. Paying half the monthly P&I every two weeks means 26 half-payments a year, which is 13 full payments instead of 12. That extra payment a year goes straight to principal. Tick the biweekly checkbox and the calculator simulates the true 2-week schedule and shows how many years earlier you finish and the interest saved. One caveat: some servicers charge for biweekly plans or just hold the money — paying 1/12 of a payment extra each month achieves nearly the same result for free.
Why does my bank's number differ slightly?
Banks compute interest with conventions that vary slightly: actual/360, US Rule, simple interest after the last payment. The PMT formula here matches the standard "actual/actual, end-of-period, equal monthly payments" model used by most fixed-rate mortgages in the US — usually within a dollar or two of the bank's quote on a typical loan.
Does this work for adjustable-rate mortgages (ARMs)?
Not directly. The current calculator assumes a fixed rate for the full term. For an ARM, run two scenarios: one at the intro rate to see the initial payment, and one at the cap rate to see the worst-case payment after rate adjustments.