Loan Calculator
Work out your loan payment, how much you can afford to borrow, or how long payoff will take, and see how extra payments cut your interest. Everything runs in your browser.
What is a Loan Calculator?
A loan calculator shows the real cost of borrowing before you sign anything. Most payment calculators answer one question: what will my payment be? This one answers three. Give it an amount, a rate, and a term, and it returns the payment. Give it a payment you can afford, and it returns the most you can borrow. Give it an amount and a payment, and it shows how long payoff will take. For each answer you also get the total interest, the total repaid, a balance chart, and a yearly repayment summary.
It works for personal loans, car loans, mortgages, student loans, business loans, and any other fixed-rate loan repaid in equal installments. You can switch between monthly, bi-weekly, and weekly payments. You can also add an extra amount to each payment and see exactly how much interest and time it saves, which helps you decide whether paying ahead is worth it.
GuideHow to use it
How the loan math works
The calculator uses the standard amortization formula for a fixed-rate, reducing-balance loan: Payment = P × r ÷ (1 − (1 + r)⁻ⁿ). Here P is the loan amount, r is the interest rate per payment period, and n is the number of payments. To find the loan amount, the same formula is rearranged to solve for P. To find the payoff time, it is solved for n using logarithms. The calculator then steps through the loan one payment at a time. It charges interest on the remaining balance, puts the rest of the payment toward principal, and repeats until the balance reaches zero. That is how a lender builds its schedule.
Why it helpsFeatures & benefits
Why extra payments save so much
Interest is charged on whatever balance is left, so every extra amount you pay lowers the balance that future interest is charged on. The effect adds up over time. Even a small extra payment made from the start can take months or years off a long loan and save a large share of the total interest. The savings note in the results compares your schedule with and without the extra payment, so you can try different amounts before you commit.
Monthly vs. bi-weekly vs. weekly payments
Switching from monthly to bi-weekly payments at the same annual rate means 26 smaller payments a year instead of 12. Interest is charged on a slightly lower balance each period, which cuts the total interest a little. Many borrowers also pay half their monthly amount every two weeks. That adds up to one extra monthly payment each year and can take years off a mortgage. To model this, set the frequency to bi-weekly and enter half your monthly payment.
Getting an accurate estimate
The results assume a fixed interest rate, equal payments, and no fees, which matches most standard installment loans. Variable-rate loans, balloon payments, origination fees, insurance, and taxes are not included. Treat the numbers as a close estimate and check the final figures against your lender's official loan disclosure. Enter the rate as a percentage (7.5, not 0.075). Use the APR if you want fees reflected in the interest rate.
Frequently asked questions
Common questions about loan payments, affordability, and interest.
The calculator uses the standard amortization formula, Payment = P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the loan amount, r the rate per payment period, and n the number of payments. Each payment covers that period's interest first, and the rest reduces the principal.
Pick "Loan amount" mode, then enter the payment you can comfortably afford, the interest rate, and the term. The calculator works backwards through the amortization formula to find the largest loan that payment can repay in full within your chosen time.
Extra payments go straight to principal, so every later payment is charged interest on a smaller balance. The results show the exact interest saved and how much sooner the loan is paid off compared with the regular schedule. Early extra payments have the biggest effect.
If a payment is equal to or less than the interest charged each period, the balance never goes down and the loan is never repaid. The calculator warns you and shows the smallest payment that covers the interest. Pay more than that amount so the principal actually starts to fall.
No. Every calculation, from the payment formula to the full repayment schedule, runs locally in your browser with JavaScript. Nothing you type is uploaded, saved, or shared, and it all disappears when you close the tab. Your financial details stay on your device.