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Financial Interstate

Loan Payment Calculator

Estimate the monthly payment on a fixed-rate loan, along with the total interest and total cost over its life. Add an optional extra monthly payment to see how much interest and time you could save.

An additional amount paid toward principal each month.

Estimated monthly payment

Total paid over the loan
Total interest

Enter your numbers above to see an estimate.

How this works

This uses the standard amortized-loan formula PMT = P·r / (1 − (1 + r)−n), where P is the amount borrowed, r is the monthly interest rate (your APR ÷ 12), and n is the number of monthly payments. At 0% interest it falls back to simply dividing the balance across the term.

When you add an extra monthly payment, the calculator simulates the payoff month by month to find the real payoff date, the interest you'd avoid, and the time you'd shave off.

What this does not include

Real loans often carry costs this doesn't model: origination or closing fees, taxes, required insurance, PMI, or a variable rate that moves over time. Those can meaningfully change the true cost.

It assumes a fixed rate and on-time payments. For a mortgage specifically, a dedicated mortgage calculator (with taxes and insurance) is coming soon.

Like this tool? The case studies go deeper.

Each issue works through a real money decision — the kind these calculators only start to answer.

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