Amortization Calculator

View a detailed loan amortization schedule with month-by-month breakdown

Last reviewed: July 2026How we build & verifyEstimate only. Verify important decisions with a qualified professional

Loan Amount ($)

Interest Rate (%)

Term (years)

yrs

How it works

Builds the full payment-by-payment schedule for a fixed-rate loan, showing how much of each instalment goes to interest and how much reduces the balance. The payment stays constant while the split shifts steadily toward principal.

Formula

Payment = P × r(1+r)^n / ((1+r)^n − 1)
Interest_k = Balance_(k−1) × r
Principal_k = Payment − Interest_k

Variables

Poriginal loan principal
rperiodic interest rate (annual rate ÷ payments per year)
ntotal number of payments
Balanceprincipal still outstanding after each payment

Worked example

Inputs: $250,000 at 6.5% annual, 30 years, monthly

r = 0.065 / 12 = 0.0054167, n = 360
(1.0054167)^360 ≈ 6.9918
Payment = 250000 × 0.0054167 × 6.9918 / (6.9918 − 1) ≈ 1,580.17
Month 1 interest: 250000 × 0.0054167 = 1,354.17
Month 1 principal: 1580.17 − 1354.17 = 226.00

Result: $1,580.17 per month; after payment 1 the balance is $249,774.00

Notes

On a 30-year loan at 6.5%, roughly 86% of the first payment is interest. The crossover point where principal exceeds interest arrives around year 18.
Total interest here is $318,861, which exceeds the amount borrowed. Shortening the term cuts that far more than shaving a fraction off the rate.
A prepayment applied to principal removes every future interest charge that principal would have generated, so early extra payments are worth far more than late ones.
Biweekly schedules make 26 half-payments a year, which equals 13 monthly payments, not 12. That is where the advertised savings actually come from.

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Frequently Asked Questions

Amortization is the gradual repayment of a loan through scheduled, equal payments. Each payment covers accrued interest first, then reduces the principal. Early payments are mostly interest; later ones are mostly principal.

Our calculator produces a month-by-month table showing the interest portion, principal portion, remaining balance, and total paid for every payment over the life of the loan.

Yes, substantially. Extra payments go straight to principal, reducing all future interest. An extra $100/month on a 30-year mortgage can save tens of thousands and shave years off the term.

How it works

Formula

Payment = P × r(1+r)^n / ((1+r)^n − 1)
Interest_k = Balance_(k−1) × r
Principal_k = Payment − Interest_k

Variables

Poriginal loan principal
rperiodic interest rate (annual rate ÷ payments per year)
ntotal number of payments
Balanceprincipal still outstanding after each payment

Worked example

Inputs: $250,000 at 6.5% annual, 30 years, monthly

r = 0.065 / 12 = 0.0054167, n = 360
(1.0054167)^360 ≈ 6.9918
Payment = 250000 × 0.0054167 × 6.9918 / (6.9918 − 1) ≈ 1,580.17
Month 1 interest: 250000 × 0.0054167 = 1,354.17
Month 1 principal: 1580.17 − 1354.17 = 226.00

Result: $1,580.17 per month; after payment 1 the balance is $249,774.00

Notes

On a 30-year loan at 6.5%, roughly 86% of the first payment is interest. The crossover point where principal exceeds interest arrives around year 18.
Total interest here is $318,861, which exceeds the amount borrowed. Shortening the term cuts that far more than shaving a fraction off the rate.
A prepayment applied to principal removes every future interest charge that principal would have generated, so early extra payments are worth far more than late ones.
Biweekly schedules make 26 half-payments a year, which equals 13 monthly payments, not 12. That is where the advertised savings actually come from.

Amortization Calculator

How it works

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Frequently Asked Questions

Amortization Calculator

How it works

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Frequently Asked Questions