π¦ Loan Calculator
Payment, total interest, and amortization for any fixed loan.
Monthly Payment
Estimates for planning only, not financial advice.
How to Use This Calculator
This calculator handles any fixed-rate loan: personal loans, auto loans, student loans, or anything else with a set payment schedule. Enter the amount, APR, and term, then optionally add an extra principal payment to see how much interest it saves.
Enter the Loan Amount, the APR (as a plain number like 6), and the Term in years. Fractional years work too, such as 2.5 for 30 months.
Optionally enter an Extra Principal amount per month to model paying the loan off early.
Read the monthly payment, total interest, total cost, and payoff date. The yearly table shows how each year splits between principal and interest.
Download the schedule as CSV to keep a record or to compare two loan offers side by side in a spreadsheet.
The Loan Amortization Formula
Amortization means the loan is paid off in equal installments, but the installments are not equal inside: early payments are mostly interest, late payments mostly principal. The formula finds the single payment amount that makes the balance hit exactly zero after n payments. If the rate is zero, the payment is simply the principal divided by the number of payments. Everything else, fees, insurance, escrow, sits outside this formula and gets added to the payment separately.
Worked Example
$100,000 loan, 6 percent APR, 30-year term (360 months). Monthly rate = 0.06 / 12 = 0.005. Payment = 100000 x 0.005 x (1.005)^360 / ((1.005)^360 - 1) = $599.55 per month. Total paid = $599.55 x 360 = $215,838, so total interest = $115,838. The first payment contains $500.00 of interest and only $99.55 of principal; the last payment contains $2.98 of interest and $596.57 of principal. That is why the same loan at 15 years (payment $843.86) costs only $51,894 in total interest: you spend far fewer years in the interest-heavy phase.
Comparing Loan Offers the Right Way
Never compare loans by monthly payment alone; compare total interest plus fees over the life of the loan. A lower payment usually means a longer term, which means more interest. When offers have different fee structures, add the fees to the total interest and divide by the loan amount to get a rough effective cost. And check for prepayment penalties before planning extra payments: most personal loans have none, but some auto and mortgage products do. A loan you can pay early is worth more than a slightly cheaper one you cannot.
Estimates for planning only, not financial advice.
Frequently Asked Questions
How is a loan payment calculated?
Every fixed loan uses the amortization formula: Payment = P x r x (1+r)^n / ((1+r)^n - 1), where P is the amount borrowed, r the monthly interest rate, and n the number of payments. For a $100,000 loan at 6 percent APR over 30 years, the monthly payment is $599.55. Each payment first covers the month's interest, and the rest reduces the balance.
Why is so much of my early payment interest?
Because interest is charged on the outstanding balance, which is largest at the start. On that $100,000, 6 percent loan, the first $599.55 payment contains $500 of interest and only $99.55 of principal. As the balance shrinks, the interest slice shrinks too, so later payments are mostly principal. Extra payments early in the loan attack the balance when it matters most.
What is the difference between APR and interest rate?
The interest rate is what the lender charges on the balance; the APR adds certain fees and spreads them across the loan, so APR is usually slightly higher. For comparing loan offers, APR is the fairer number because it includes the fees. This calculator uses the APR you enter as the effective rate for the amortization math.
How much do extra payments save?
More than most people expect, because every extra dollar skips all the future interest it would have generated. Adding $100 a month to a $20,000, 8 percent, 5-year loan pays it off about 7 months early and saves roughly $700 in interest. Enter an extra payment in this calculator to see your exact savings and new payoff date.
Is a longer term ever worth it?
Sometimes, for cash-flow reasons. Doubling the term from 5 to 10 years on a $20,000, 8 percent loan cuts the payment from $405.53 to $242.66 but raises total interest from $4,332 to $9,119. If the lower payment keeps you from missing payments during lean months, the insurance value can be worth it, especially if you pay extra when you can.