Every amortizing loan — whether it is a personal loan, an auto loan, a student loan, or a small-business term loan — boils down to a single question: what will each monthly bill actually be, and how much of it is interest? This free loan calculator estimates your fixed monthly payment, the total interest you will pay over the life of the loan, and the grand total you hand back to the lender. Type in the amount you want to borrow, the annual interest rate, and the repayment term, and the numbers update instantly.
Because the math is the same no matter what the money is for, the same tool works for comparing offers from different lenders, checking whether a longer or shorter term fits your budget, and modeling how much an extra payment each month could save you.
How to Use
- Enter the Loan Amount — the principal you intend to borrow. This is the starting balance; the calculator does not add taxes, fees, or down payments.
- Set the Interest Rate (APR). Use the annual percentage rate, not a monthly rate. If a lender quotes you a range, run the low and high ends to see how sensitive your payment is.
- Choose the Loan Term in years. A shorter term raises the monthly payment but almost always cuts total interest dramatically; a longer term lowers the monthly bill but costs more over time.
- Optionally add an Extra Monthly Payment. This is money you choose to pay beyond the required bill, and it goes straight against the principal. Even a modest recurring amount can shorten the loan by months or years.
- Read the result card: your Monthly Payment, Total Interest Paid, and Total Amount Paid. Add an extra payment and watch the interest line drop.
The payment uses the standard amortization formula used by spreadsheets and lenders:
M = P × r(1 + r)ⁿ / ((1 + r)ⁿ − 1)
Where M is the monthly payment, P is the loan amount, r is the monthly interest rate (the APR divided by 12), and n is the total number of monthly payments (years times 12). This is the same closed-form PMT function found in Excel, Google Sheets, and open-source finance libraries. If the interest rate is 0%, the formula would divide by zero, so the engine simply splits the principal evenly across the number of months.
Examples
Example 1 — A straightforward personal loan. You borrow $20,000 at a 6.5% APR and repay it over 5 years (60 monthly payments). The monthly rate is 6.5% / 12 = 0.005417. Plugging into the formula gives a monthly payment of $391.32. Over the full term you pay back $23,479.38 in total, meaning the interest alone is $3,479.38 — about 17% of the original amount.
Example 2 — Stretching the term. Keep the same $20,000 at 6.5% but extend the term from 5 years to 7 years (84 payments). The monthly payment falls to roughly $294, which eases the monthly budget, but the total interest climbs to about $4,696. The lower bill is comfortable, but you are paying interest for an extra two years.
Example 3 — The prepayment effect. On the same $20,000 loan at 6.5% over 5 years, adding just $50 to each monthly payment shaves several months off the term and saves a meaningful chunk of interest, because every extra dollar immediately shrinks the balance on which future interest is charged. Use the Extra Monthly Payment slider to see your own savings.
Example 4 — A large balance. On a $1,000,000 loan at 6.5% over 30 years, the monthly payment is about $6,320.68, and total interest reaches roughly $1,275,445 — more than the original principal. Running this figure before signing prevents payment shock later.
FAQ
How is my monthly loan payment calculated?
The payment uses the standard amortization (PMT) formula: M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly interest rate (the annual APR divided by 12), and n is the number of monthly payments (the loan term in years times 12). This is the same formula spreadsheets and lenders use.
What is the difference between APR and the interest rate?
The nominal interest rate is the cost of borrowing the principal. The APR folds in certain fees and charges so you can compare offers on a like-for-like basis. For this calculator, enter the APR quoted by the lender for the most realistic all-in estimate.
Should I choose a shorter or longer loan term?
A shorter term raises your monthly payment but usually qualifies you for a lower rate and saves you tens of thousands in interest. A longer term lowers the monthly bill but costs more over the life of the loan. Choose the shortest term whose payment still fits comfortably in your budget.
Does paying extra each month actually save money?
Yes. Every extra dollar paid toward principal reduces the balance on which future interest is charged, so the savings compound over time. Even an extra $25 or $50 per month can cut months or years off the loan. Confirm your loan has no prepayment penalty before planning around this.
What happens if the interest rate is 0%?
Some financing offers carry a 0% promotional rate. In that case there is no interest to compound, so the loan simply splits the principal evenly across the number of monthly payments — for example, $20,000 over 60 months is $333.33 per month with $0 in interest.
Can I use this calculator for any kind of loan?
Yes. Because every amortizing installment loan uses the same PMT math, this calculator works for personal loans, auto loans, student loans, and small term loans alike. It is not tailored to mortgages with taxes, insurance, or escrow — use a dedicated mortgage tool for that.
Disclaimer
This loan calculator is provided for informational purposes only and does not constitute financial, lending, or tax advice. Estimates are based on the inputs you enter and the standard amortization formula; actual offers vary by lender, credit profile, fees, and program. Always confirm your final payment and terms directly with a licensed lender before you commit to a loan.