Loan Calculator
Work out the payment, loan amount, term or interest rate of any fixed-rate loan, with monthly, biweekly or weekly payments, fees and APR, extra payments and a full amortization schedule.
How it works
M = P × i ÷ (1 − (1 + i)^−n) · i = annual rate ÷ payments per year (or (1 + R ÷ m)^(m ÷ p) − 1 for other compounding) · n = years × payments per year · Total interest = total paid − P
P is the amount borrowed, i the interest rate for one payment period and n the number of payments. With monthly payments and monthly compounding, i is simply the annual rate ÷ 12. If interest compounds on a different schedule than you pay — daily, quarterly, twice a year like Canadian mortgages — the calculator first converts the annual rate into the equivalent rate per payment period. Each payment covers that period’s interest on the remaining balance and the rest reduces the principal, so early payments are mostly interest. The same equation can be solved for any one unknown: the payment, the amount you can borrow for a given payment, how long a payment takes to clear the loan (rounded up to whole payments, with a smaller last payment), or the interest rate hidden in a quoted payment (found by trial, since there is no closed formula). Besides the standard equal-payment loan, you can model equal-principal loans, interest-only loans with the principal due at the end, and deferred loans repaid in one lump sum. Upfront fees do not change the payment, but they mean you receive less than you repay, so the APR — the rate that matches the money you actually got to the payments you make — is higher than the interest rate. Extra payments go straight to principal and are compared with the same loan without them.
Worked example
Borrow $20,000 at 8% for 5 years with monthly payments: i = 0.08 ÷ 12 = 0.006667 and n = 60, so M = 20,000 × 0.006667 ÷ (1 − 1.006667^−60) = $405.53. Over 60 payments you repay $24,331.67, so interest is $4,331.67. With a $400 origination fee the APR rises to about 8.86%. Paying the same loan every two weeks instead (130 payments, still compounded monthly) gives a payment of $186.83. Adding $50 to every monthly payment clears the loan in 53 payments (4 years 5 months) and saves $590.24 of interest. Going the other way, $405.53 a month for 5 years at 8% supports a $20,000 loan, and $405.53 a month on $20,000 for 60 payments implies an 8% rate.
Sources: CFPB — What is the difference between a loan interest rate and the APR? · CFPB — Regulation Z, Appendix J (annual percentage rate computations)
Frequently asked questions
Can it work out the loan amount, term or rate instead of the payment?
Yes. Pick what to calculate at the top. “Loan amount” tells you how much a payment you can afford will borrow, “Term” shows how many payments a given amount takes (the last one is usually smaller), and “Interest rate” finds the rate built into a quoted payment, which is handy for checking dealer or store financing.
What changes with biweekly or weekly payments?
The rate is split into smaller periods and there are more payments a year. Paying every two weeks means 26 payments, which is a little more than 12 monthly payments’ worth each year, so the loan ends slightly sooner and costs less interest. The compounding setting under More options controls how the annual rate is turned into a per-payment rate.
Is APR the same as the interest rate?
No. The interest rate sets the payment. APR also counts upfront fees such as an origination fee, spreading them over the term, so it is higher whenever there are fees. Enter the fees under More options to see the APR and the amount you actually receive. Use APR to compare offers.
How much do extra payments save?
Every extra dollar cuts the principal right away, so it stops earning interest for the rest of the loan. Turn on extra payments to add an amount to each payment, once a year or one time, and the calculator shows the interest saved, the new payoff date and both balance lines. Check that your lender has no prepayment penalty.
What are equal-principal, interest-only and deferred loans?
With equal principal you repay the same slice of principal each time plus interest, so payments start high and fall. Interest-only loans charge just the interest each period and the whole principal is due at the end. A deferred loan has no payments at all until maturity, when the principal and all compounded interest are due in one sum.
Does this work for personal, auto and student loans?
Yes — any fixed-rate loan with regular payments uses this math. For car-specific inputs such as trade-in and sales tax, or student-loan plans, use the dedicated calculators linked below. Variable rates are not modeled.
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This is an educational estimate, not financial advice. Lenders use their own rounding, fees and credit terms — confirm exact figures with your lender or a licensed advisor.