Most mortgage calculators give you one number — the monthly principal and interest — and stop. But that's not what you actually pay, and it's not the number that decides whether a loan is a good idea. A free mortgage calculator should show you three things the bank rarely leads with:
- Your full monthly payment including taxes, insurance and PMI (PITI)
- The total interest you'll pay over the life of the loan
- How much a small extra payment changes both
Let's walk through all three with real numbers.
How a monthly mortgage payment is calculated
The principal-and-interest portion uses the standard amortization formula:
M = P × r × (1+r)^n / ((1+r)^n − 1)
- P = loan amount (home price − down payment)
- r = monthly interest rate (APR ÷ 12 ÷ 100)
- n = number of months
You don't calculate this by hand. The calculator does it instantly and shows the full amortization schedule below the result.
A real example
Home price: $400,000
Down payment: 20% ($80,000) → loan: $320,000
Rate: 6.39% · Term: 30 years
- Principal & interest: ~$2,000/month
- Total interest over 30 years: ~$400,000 — more than the loan itself
That last number is the one that should change how you think about the loan. You borrow $320,000 and pay back roughly $720,000.
How to calculate yours
- Open the free mortgage calculator
- Enter the home price and drag the down payment slider
- Add the APR and pick a 15, 20 or 30-year term
- See your monthly payment, total interest, and payoff date instantly
PITI — what you actually pay each month
Principal and interest is only part of it. Expand the taxes, insurance & HOA section to see your full PITI payment:
| Component | Monthly |
|---|---|
| Principal & Interest | $2,000 |
| Property Tax ($4,800/yr) | $400 |
| Home Insurance ($1,800/yr) | $150 |
| Total PITI | $2,550 |
If your down payment is under 20%, the calculator automatically adds PMI (private mortgage insurance, ~0.5% of the loan per year — about $133/month on this loan) until you reach 20% equity.
Extra payments — the part that saves real money
Here's where it gets interesting. Add just $200/month extra to that $320,000 loan:
- Without extra: 30 years, ~$400,000 interest
- With $200/month extra: paid off in ~23.5 years — about 6.5 years sooner — and ~$100,000 less interest
Two hundred dollars a month, the price of skipping one dinner out a week, buys back six and a half years and a hundred grand. Enter your own numbers to see the exact saving.
15-year vs 30-year
Use the term toggle to compare. A 15-year mortgage has a higher monthly payment but a lower rate and far less total interest, because you repay the principal in half the time. Seeing both side by side makes the trade-off concrete before you commit.
Works in 5 currencies
Switch between USD, GBP, EUR, CAD and AUD for US, UK, EU, Canadian and Australian mortgages. The mortgage rate news panel below the calculator shows the current US 30-year fixed rate plus UK, EU and Australian central-bank rates, updated weekly.
Related Tools
- debt snowball vs avalanche payoff calculator free — once the mortgage is set, plan paying down your other debts; it compares both methods and shows your debt-free date
- loan EMI calculator with full amortization schedule — for car, personal or education loans, with a reverse mode that finds the maximum loan your budget supports
- convert currencies with live exchange rates free — for international buyers comparing a mortgage priced in another currency
Run your own numbers — taxes, insurance, PMI, extra payments and the full amortization schedule — with the free mortgage calculator →
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