Loan calculator: monthly payment, interest and total cost
This loan calculator shows the monthly payment, the interest you will pay across the full term, and how the balance falls year by year. Before you sign any mortgage, car loan or personal loan, it is worth seeing the total cost rather than only the monthly figure.
What is the loan calculator?
A loan calculator works out the fixed monthly payment that clears a loan over a set term. Early payments are mostly interest and later payments are mostly principal, which is why long loans cost far more than the headline amount suggests. This calculator also includes an overpayment simulator, so you can see how a single lump sum shortens the term and cuts total interest.
How the loan calculator works
Payment = [P × R × (1 + R)^N] / [(1 + R)^N − 1]- P: loan principal
- R: monthly interest rate (annual rate ÷ 12)
- N: number of monthly payments
Worked example
Borrow $500,000 over 20 years at 8.5%. The monthly payment works out near $4,340, and across 240 payments you repay about $1.04 million, which means roughly $540,000 is interest, more than the loan itself. Overpay $50,000 once and the calculator shows the loan ending years early with a large share of that interest saved.
How to use it
- Enter the loan amount, interest rate and term.
- Read the monthly payment and, more importantly, the total interest.
- Add an optional one-time overpayment to test the impact.
- Use the balance chart to see how the debt falls over time.
Good to know before you rely on it
- The monthly payment is only part of the cost. Arrangement fees, insurance and early repayment charges add up, so ask for the total cost of credit.
- Overpaying early saves far more interest than overpaying near the end, because early payments are mostly interest.
- A variable rate can move. If your loan is not fixed, stress test the payment at a rate two or three points higher.
- A longer term lowers the monthly payment but raises total interest sharply. The comfortable monthly figure is often the expensive one overall.
Why Thewealthora’s loan calculator is different
- The loan calculator surfaces the total interest figure that lenders rarely put in front of you.
- An overpayment simulator shows the months saved and the interest cut, instantly.
- The declining balance chart makes a 20 year commitment tangible.
Pair it with the compound interest calculator, the currency converter, or open live markets and our investing guides.
Sources and further reading
For the underlying concepts, see the U.S. Consumer Financial Protection Bureau on loans and interest.
Frequently asked questions
How is a monthly loan payment calculated?
The payment is set so the loan clears exactly at the end of the term. It combines interest on the outstanding balance with a share of the principal, and because the balance falls, the interest portion shrinks every month.
Is EMI the same as a monthly loan payment?
Yes. Equated monthly instalment, or EMI, is the term used in India and the Gulf for the same fixed monthly repayment this calculator produces.
How can I reduce my total interest?
Three levers: a shorter term, which raises the payment but cuts interest sharply, overpayments toward principal whenever allowed, and refinancing when rates fall meaningfully below your current rate.
Why is total interest sometimes as large as the loan itself?
Over terms of 20 to 30 years, interest accrues against you the whole time. The calculator shows the interest share so the trade-off is visible before you commit.
This tool is for education, not personalised financial advice. Results are projections based on your inputs, not guarantees.
More free tools
Keep going: check live stock market prices, read our investing guides for beginners, or catch up on today's finance news.