Amortization Calculator
Calculate your fixed monthly loan payment, total interest, total of all payments, and payoff date from a loan amount, interest rate, and term.
How It's Calculated
Formula
\text{Payment} = \dfrac{P \times r \times (1 + r)^n}{(1 + r)^n - 1}An amortization schedule breaks every loan payment into its two components — interest and principal — for every period of the loan's life, from the first payment to the last. This calculator computes the full monthly schedule internally from your loan amount, interest rate, and term, using the standard fixed-rate (ordinary annuity) amortization formula: it solves for the constant monthly payment that pays off the loan's principal exactly by the final payment. Early in the schedule, most of each payment goes toward interest, because interest is charged on a still-large remaining balance; as the balance shrinks month by month, a growing share of the fixed payment goes toward principal instead, until the very last payment finishes paying off whatever balance remains. The Start Month and Start Year fields don't change any of that math — they only label which calendar month each payment falls in, so "Payment 1" can be shown as, say, "April 2026" instead of an anonymous number. Per the standard ordinary-annuity convention, the first payment is due one full calendar month after the start month/year you enter (so a March 2026 start means payment 1 is due April 2026, and a December 2026 start rolls over to January 2027).
Worked Examples
$250,000 loan, 6% annual rate, 30-year term (starting March 2026)
- Principal P = $250,000, annual rate 6% → monthly periodic rate r = 0.06 / 12 = 0.005
- Term: 30 years → n = 360 monthly payments
- Fixed monthly payment = P × r × (1+r)^360 / ((1+r)^360 − 1) = $1,498.88
- Schedule excerpt (Month, Interest, Principal, Ending Balance):
- Payment 1 (April 2026): interest $1,250.00, principal $248.88, balance $249,751.12
- Payment 2 (May 2026): interest $1,248.76, principal $250.12, balance $249,501.00
- Payment 3 (June 2026): interest $1,247.51, principal $251.37, balance $249,249.63
- Payment 180, the halfway point (March 2041): interest $891.14, principal $607.74, balance $177,621.13 — notice interest is already well below the principal portion by the midpoint
- Payment 360, the final payment (March 2056): interest $7.44, principal $1,488.01, balance $0.00 — the final payment's principal is set to exactly whatever balance remains, so the schedule always reconciles to a precise $0.00
- Totals over the full term: total principal = $250,000.00 (equals the original loan amount), total interest ≈ $289,593.37, total of all payments ≈ $539,593.37
$60,000 loan, 5% annual rate, 10-year term (starting January 2026)
- Principal P = $60,000, annual rate 5% → monthly periodic rate r = 0.05 / 12 ≈ 0.0041667
- Term: 10 years → n = 120 monthly payments
- Fixed monthly payment = P × r × (1+r)^120 / ((1+r)^120 − 1) = $636.39
- Payment 1 (February 2026): interest $250.00, principal $386.39, balance $59,613.61
- Payment 60, the halfway point (January 2031): interest $142.57, principal $493.82, balance $33,723.13
- Payment 120, the final payment (January 2036): interest $2.64, principal $634.20, balance $0.00
- Total interest over the full term ≈ $16,367.25 — a shorter term and lower rate than the first example mean far less total interest, even though the payment is a much smaller monthly amount
Frequently Asked Questions
Why does most of my early payments go toward interest instead of principal?
Interest for each payment is calculated on the balance still owed at that point, not on the original loan amount. Early on, the balance is close to the full loan amount, so the interest portion is largest. Every payment is the same fixed amount, so whatever's left after interest goes to principal — which is small at first and grows every month as the balance (and therefore the interest charge) shrinks.
Does the Start Month/Start Year change my payment amount?
No. Start Month and Start Year only affect the calendar labels shown for each payment (which month a given payment falls in) — they have no effect on the payment amount, the interest/principal split, or the total interest paid. The payment math depends only on loan amount, interest rate, and term.
Why is my first payment dated the month after my start month?
This follows the standard "ordinary annuity" convention used for virtually all conventional loans: a payment is due at the END of a period, not the beginning. If your loan originates in March, the first full month of interest accrues during March, and that first payment becomes due at the end of that period — labeled as April. A December origination rolls over into a January first payment the following year.
Why does the last payment amount look slightly different from the others?
This calculator's schedule reconciles to an exact $0.00 final balance, matching how real bank and lender amortization statements are produced: every row's interest and principal are rounded to the cent, and the final payment's principal is set to whatever balance is actually left (rather than the formulaic payment-minus-interest amount), so tiny rounding differences don't accumulate into a balance that never quite reaches zero. The result is a final payment that may differ from the regular payment by a few cents to a couple of dollars — a normal, expected "true-up" payment.
Can I see the full month-by-month schedule, not just an excerpt?
Yes. The full schedule — every payment, with its date, payment amount, principal, interest, and remaining balance — is available below the summary results. For a long-term loan it's collapsed by default ("View full schedule") so the page doesn't load hundreds of rows before you've asked for them; click it to see every row.
Does this work for any type of fixed-rate loan?
Yes — the underlying fixed-rate amortization math is the same one used for mortgages, auto loans, and personal loans. This calculator assumes monthly payments with no extra payments, fees, taxes, or insurance folded in; for mortgage-specific extras like property tax and homeowners insurance, use the dedicated Mortgage Calculator instead.