Mortgage & loan tool
Estimate your monthly payment, total interest, and payoff date for a fixed-rate loan. Add an extra monthly payment to see how much interest you save and how many months you shave off the term — all results update instantly in your browser.
Payment breakdown
Over the full loan term, every dollar you repay is either principal (the amount borrowed) or interest (the lender's charge). The chart shows the split for your current inputs.
| Extra / month | Monthly total | Total interest | Payoff | Saved |
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The biggest loan you will sign
A mortgage is a decades long promise, and the monthly figure printed on an offer is only part of the story. The sections below show what makes up the payment, why a small rate difference matters so much, and which costs sit outside the loan itself.
A standard mortgage payment joins two moving parts: principal, the amount that pays down what you borrowed, and interest, the cost of borrowing it. Early in the loan almost all of each payment is interest, and only slowly does a larger share go toward the principal. Our calculator shows the monthly figure together with the total interest across the whole term, which is often the number that surprises first time buyers once they see how many years of interest are built into the schedule.
Because a mortgage runs for decades, even a small difference in the rate compounds into a large swing in total cost. A loan of a few hundred thousand at a rate that is one point higher can cost tens of thousands more over its life, money that buys no extra house. Comparing offers by total interest paid, not just by the monthly number, gives a clearer picture of what each lender is really charging, and helps you decide whether paying points upfront to lower the rate is worth it.
The loan term sets the pace. A shorter term raises the monthly payment but shrinks the total interest, while a longer term lowers each payment at the cost of far more interest overall. A thirty year loan is the most common because the monthly burden feels manageable, but a borrower who can afford the higher payment of a fifteen or twenty year loan usually saves a substantial sum. Our tool lets you test both and see the lifetime difference side by side.
The principal and interest are only part of what homeowners actually pay. Property taxes, homeowner insurance, and sometimes mortgage insurance are commonly collected alongside the monthly payment into an escrow account, so the true housing cost is higher than the loan payment alone. Budgeting only for principal and interest can leave a painful gap, which is why it helps to add those recurring costs when judging whether a home truly fits your monthly income.
A worked example
Abstract explanations are easier to trust once you watch them on a real loan. The two examples below use round figures so the lifetime cost difference is impossible to miss.
Take a $300,000 loan over thirty years. At a 6 percent rate the monthly principal and interest is about $1,799, and total interest across the term is roughly $347,000. At 7 percent the monthly payment rises to about $1,996, and total interest climbs to about $418,000. The single point of difference costs more than $70,000 over the life of the loan, which is why comparing total interest, not just the monthly figure, changes how you shop.
Switch that same loan to a twenty year term at 6 percent and the monthly payment becomes about $2,149, but total interest falls to roughly $215,000. You pay more each month yet save over $130,000 in interest compared with the thirty year loan. Whether that trade is worth it depends on your cash flow, but the calculator makes the lifetime difference impossible to miss.
FAQ
Fixed-rate amortizing loans use the formula M = P × r × (1+r)n ÷ ((1+r)n − 1). P is the principal, r is the monthly rate (annual rate ÷ 12 ÷ 100), and n is the number of monthly payments (years × 12). Early payments are mostly interest; later payments are mostly principal.
No. This calculator covers principal and interest. Property taxes, homeowners insurance, HOA dues, and PMI are location- and lender-specific, so add your lender's escrow estimate on top of the P&I figure shown here.
Every extra dollar shortens the principal earlier, so total interest falls and the payoff date moves forward. The comparison table quantifies it for your rate and term. Whether that beats investing the same cash depends on your expected returns and need for liquidity — some mortgages also carry prepayment penalties, so check your note.
A 15-year term usually has a lower rate and dramatically less total interest, but a higher required monthly payment. Run both terms in the calculator and compare the "Total of payments" figure — that is the true lifetime cost difference.
ARM payments change when the rate resets, so a single fixed formula cannot describe the whole loan. This calculator is accurate for fixed-rate loans and gives a reasonable starting estimate for ARMs during the initial fixed period.
No. All math runs locally in JavaScript. No amounts, rates, or personal details are uploaded, stored, or shared.
Disclaimer
Results are educational estimates only and are not loan offers, financial, tax, or legal advice. Actual payments depend on lender terms, escrow, PMI, fees, and rate locks. Confirm exact figures with your lender.