UtilityBaseCalculators
Loan Calculator
Monthly payment, total interest, and payoff schedule — with extra-payment math.
Updated July 8, 2026
How to use the loan calculator
- 1Enter the loan amount, APR, and term in years.
- 2Read the monthly payment, total interest, and total paid.
- 3Try an extra monthly payment and watch the payoff date and interest savings move.
- 4Open the year-by-year table to see how the balance actually declines.
Common uses
- Working out what a car payment really costs before visiting a dealer
- Comparing loan offers with different rates and terms on total cost
- Deciding whether extra monthly payments are worth it on an existing loan
- Understanding amortization for a personal finance class or first big purchase
Frequently asked questions
How is the monthly payment calculated?
The standard amortization formula: payment = P·r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the principal, r the monthly rate (APR ÷ 12), and n the number of months. Each payment covers that month's interest first; the remainder reduces principal, which is why the interest portion shrinks over time.
Why do extra payments save so much interest?
Every extra dollar goes straight to principal, and all future interest is charged on the now-smaller balance — the savings compound for the loan's whole remaining life. Early extras matter most: $100/month extra on a $25,000, 7.5%, 5-year loan pays it off roughly 8 months early. The calculator runs your exact numbers.
Does this work for mortgages?
For the principal-and-interest portion, yes — the math is identical. A real mortgage payment usually adds property tax, homeowners insurance, and sometimes PMI in escrow, so expect the true monthly outlay to be meaningfully higher than the P&I figure here.
What's the difference between APR and interest rate?
The interest rate is the cost of borrowing; APR bundles in mandatory fees to give a truer annual cost, which is why APR is the number to compare between lenders. This calculator treats your input as the effective annual rate with monthly compounding.
About this tool
The loan calculator computes the monthly payment for any amortized loan — car, personal, student, or mortgage principal-and-interest — from amount, APR, and term, along with the two numbers lenders don't headline: total interest and total amount paid. The extra-payment field is where it earns its keep: add any monthly amount and see exactly how much earlier the loan dies and how the interest bill shrinks, computed by running the actual amortization month by month rather than a formula approximation. A year-by-year table shows payment, interest, and remaining balance, making visible how early payments are mostly interest and late ones mostly principal.
Like everything on UtilityBase, the loan calculator runs entirely in your browser — nothing you enter is uploaded or stored on a server. It's free to use with no account required. Browse more calculators here.
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