Finance

Mortgage calculator

Calculate monthly mortgage payments, total interest, and the full amortisation schedule for any home loan. Optionally add taxes and insurance to see total housing costs.

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How the mortgage calculator works

A mortgage calculator takes a home price, down payment, interest rate, and loan term, and returns the monthly principal-and-interest payment using the standard amortizing-loan formula. Enter optional property tax and homeowners insurance to see the full PITI (principal, interest, taxes, insurance) monthly cost — closer to what you'll actually write a check for each month.

The amortization schedule below shows, year by year, how much of each payment goes to interest versus principal. Early in the loan, most of the payment is interest. As the balance drops, more goes to principal — until the final payments are almost entirely principal. Paying a little extra each month accelerates this crossover and can save tens of thousands in interest.

P&I vs PITI

Principal-and-interest is what you owe the lender. PITI adds property tax and homeowners insurance — two costs many buyers underestimate. On a $400k home, tax and insurance alone can add $500–800 to the monthly payment, so it's worth including them when budgeting.

The mortgage formula

The standard amortization formula is M = P × [r(1 + r)^n] ÷ [(1 + r)^n − 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12). This produces a level payment that fully amortizes the loan by the end of the term.

M = P × [r(1+r)^n] / [(1+r)^n − 1]

Common Uses

FAQ

How much should I put down?

A 20% down payment is traditional and avoids private mortgage insurance (PMI) in the US. With less, lenders typically require PMI until you reach 20% equity. 3–10% down is common for first-time buyers — the trade-off is a higher monthly payment and PMI until you build equity.

What is PITI?

PITI stands for Principal, Interest, Taxes, and Insurance — the four components of a typical monthly mortgage payment. Taxes and insurance are often collected alongside principal and interest into an escrow account, so many homeowners only write one check per month covering all four.

Does paying extra each month really help?

Yes. Any amount above the scheduled payment goes entirely to principal, reducing future interest. Even small extra payments — $100/month on a $300k loan — can cut 4–5 years off a 30-year mortgage and save tens of thousands in interest. Confirm with your lender that extra payments apply to principal, not to prepaying future scheduled payments.

15-year vs 30-year: which is better?

A shorter term (15 vs 30 years) means higher monthly payments but dramatically less total interest. On a $300k loan at 6%, a 30-year mortgage pays $348k in interest; a 15-year mortgage pays only $155k — less than half — because the principal is repaid much faster.

Does the mortgage calculator store my financial data?

No. All calculations run entirely in your browser. Your loan details are never sent to a server or stored after you close the page.

What is the difference between principal and interest in a mortgage payment?

Each payment has two parts: principal (which reduces your outstanding loan balance) and interest (the lender's fee). Early payments are mostly interest; the principal share grows over time as the balance decreases.

All calculations run entirely in your browser. Nothing is sent to a server.

By the Numbers

Sources & Further Reading