Loans
Loan Interest Calculator
Find out exactly how much interest you'll pay over the life of any loan — and what percentage of your total repayment goes to the lender.
🔒 All calculations happen instantly in your browser. No data is sent to any server.
How the calculation works
Monthly Payment = P × r(1+r)ⁿ ÷ [(1+r)ⁿ − 1]
Total Paid = Monthly Payment × n (total months)
Total Interest = Total Paid − Principal
Example: $200,000 mortgage at 7% over 30 years → Monthly = $1,331 → Total paid = $479,017 → Total interest = $279,017 (139% of the original loan)
Frequently Asked Questions
- Dramatically. A $300,000 mortgage at 6% over 30 years costs $347,515 in interest. At 7% it costs $418,527 — an extra $71,012 for just a 1% rate increase. Always shop for the lowest rate you qualify for.
- Yes — both by paying less total interest and by receiving a lower rate (shorter-term loans typically carry lower rates). A 15-year mortgage at 6.5% on $300,000 costs $176,000 in interest vs. $347,000 for a 30-year term — saving $171,000.
- Yes. Even one extra monthly payment per year (13 instead of 12) on a 30-year mortgage can cut the term by 4–5 years and save tens of thousands in interest. Use the Extra Payment Loan Calculator to model this.
- On a 30-year loan, total interest often equals or exceeds the principal. A $300,000 loan at 7% costs $418,527 in interest alone. This is why 15-year mortgages and extra payments are so powerful — they dramatically reduce this compounding cost.
- No — credit cards use daily periodic rate (APR ÷ 365) on the average daily balance and compound monthly. They're revolving, not amortizing. The Credit Card Payoff Calculator handles this correctly.