Loan Calculator
Calculate monthly payments, total interest, and amortization for any loan.
About This Tool
Estimate monthly payments and total cost for personal loans, mortgages, car loans, or any fixed-rate loan. Enter the principal amount, annual interest rate, and loan term to get an instant breakdown of monthly payment, total interest paid, and total amount repaid. Everything runs in your browser with no external dependencies.
What you provide
Loan amount, annual interest rate, and loan term in years or months
What you get
Monthly payment, total interest, total repayment amount, and amortization summary
How to Use
- Enter the loan amount (principal) you want to borrow.
- Set the annual interest rate and loan term in years.
- Click Calculate to see your monthly payment, total interest, and repayment breakdown.
Understanding Your Monthly Payment
Every fixed-rate loan payment is split between interest and principal, but the ratio shifts dramatically over time. In the first month of a 30-year mortgage, roughly 80% of your payment goes to interest and only 20% reduces the balance. By month 300, the ratio has flipped — most of the payment is principal. This is amortisation: the lender front-loads the interest because the outstanding balance is highest at the start, and the interest owed is calculated as (remaining balance × monthly rate) at each period.
The practical implication is that extra payments made in the early years of a loan have a disproportionate impact. A $100 extra payment in month 12 reduces the principal that interest accrues on for the remaining 348 months. That same $100 paid in month 300 saves you only 2-3 months of interest. If you have any flexibility, paying extra early — even irregular lump sums — will reduce total interest cost more than the same total amount paid steadily over the life of the loan.
APR (Annual Percentage Rate) is a more accurate cost measure than the nominal interest rate because it includes fees: origination charges, mortgage points, and closing costs. Two loans with identical nominal rates can have meaningfully different APRs. Always compare APRs when shopping loans, and remember that the APR assumption is that you hold the loan to maturity — if you plan to sell or refinance in 5-7 years, a lower-rate loan with higher upfront fees may cost more in practice.
Impact of Extra Monthly Payments
| Extra Payment | Years Saved | Interest Saved | Total Paid |
|---|---|---|---|
| $0 (baseline) | 0 years | $0 | $682,633 ($300K @ 6.5% / 30yr) |
| $50/month extra | ~1.5 years | ~$27,000 | ~$655,600 |
| $100/month extra | ~2.5 years | ~$48,000 | ~$634,600 |
| $200/month extra | ~4.5 years | ~$82,000 | ~$600,700 |
| $500/month extra | ~8.5 years | ~$145,000 | ~$537,600 |
| $1,000/month extra | ~12.5 years | ~$196,000 | ~$486,600 |
Before You Borrow
- Compare APR, not just the nominal interest rate — APR includes fees and reflects the true annual cost of the loan.
- Check for prepayment penalties before committing to a loan if you plan to pay it off early or refinance within a few years.
- Factor in property taxes and homeowner's insurance for mortgages — PITI (Principal, Interest, Tax, Insurance) is the real monthly cost, often 20-30% higher than the principal-and-interest payment alone.
- Model a 15-year vs 30-year term side by side — a 15-year loan typically carries a lower rate and dramatically less total interest, though monthly payments are higher.
- Get pre-approved before shopping — it locks your rate window and shows sellers you are a serious buyer, without a hard credit pull from every lender.
- Understand fixed vs adjustable rates — a fixed rate is predictable for budgeting; an ARM may start lower but resets periodically and can increase substantially if market rates rise.
Frequently Asked Questions
- How is the monthly payment calculated?
- The calculator uses the standard amortization formula: M = P × r(1+r)^n / ((1+r)^n − 1), where P is the principal, r is the monthly interest rate, and n is the total number of payments. This gives you the fixed monthly payment for a fully amortizing loan.
- Does this work for mortgages and car loans?
- Yes. The formula applies to any fixed-rate, fully amortizing loan including mortgages, auto loans, personal loans, and student loans. Just enter the correct amount, rate, and term.
- Is this tool free to use?
- Yes. This tool runs entirely in your browser with no account required. Your data never leaves your device.
- What if my interest rate is 0%?
- With a 0% interest rate, the calculator simply divides the loan amount by the number of months. No interest is charged, so the total repayment equals the principal.
- Does this work on mobile?
- Yes. The tool is fully responsive and works on any device with a modern browser.
Learn More
How Loan Amortization Works: Formulas, Examples, and Strategies
Learn the amortization formula, how interest and principal split over time, and strategies to reduce total interest paid on mortgages and loans.
6 min read