TheCalculatory
Financial · Borrowing & Debt Formula verified

Loan Calculator

Work out your monthly payment, total interest, and full amortization schedule. Add an extra monthly payment to see how much sooner the loan is paid off.

Presets
$
$1k$50k$100k+
%
0%12%25%
yrs
0.5 yr15 yrs30 yrs
$ /mo
$0$500$1,000
Quick adjustments
On-screen number pad
Tap to type into the highlighted field
Monthly payment
$489.15
5 years payoff time
Principal
$25,000.00
85.2% of total paid
Total interest
+$4,349.22
14.8% of total paid
Principal Interest

Step-by-step proofCheck by hand
This is an estimate, not a loan offer. It covers principal and interest only and excludes fees, taxes, insurance and lender-specific terms. Actual payments depend on your lender's terms. Consult a qualified financial professional or your lender before making borrowing decisions.
Visual breakdown

How the balance pays down

Remaining balance Cumulative interest

The solid line is what you still owe; the dashed line is interest paid so far. The interest portion of a fixed payment falls as the balance shrinks; it is not necessarily the largest portion of a payment.

Annual amortization summary

How each payment splits between principal and interest
Year Starting balance Principal paid Interest paid Ending balance

How a loan payment is calculated

A standard amortizing loan has a fixed scheduled monthly payment. The final payment may be smaller, but the mix inside it changes: interest is calculated on whatever balance remains. Interest takes a larger share early in the schedule and a smaller share later, but does not always exceed principal. That shift is called front-loading, and it is not a fee or a penalty — it is a direct consequence of interest being charged on the current balance.

Because the balance falls every month, the interest portion falls with it and the principal portion grows to keep the total payment constant. By the final payment, almost all of it is principal.

Extra payments compound in your favor
An extra dollar toward principal removes that dollar from every future interest calculation for the rest of the loan — not just the current month. Paid early, it is worth more than the same dollar paid late.
This is principal and interest only
Mortgages in particular often bundle property tax and insurance into the monthly payment through an escrow account. This calculator does not include that — check your lender's disclosure for the full payment.

The formula

M = P × [r(1+r)n] ÷ [(1+r)n − 1]
  • M — monthly payment
  • P — loan principal (amount borrowed)
  • r — monthly interest rate (annual rate ÷ 12), as a decimal
  • n — total number of monthly payments

Worked example

A $25,000 loan at 6.5% annual interest over 5 years: r = 0.065 ÷ 12 = 0.0054167, n = 60 payments. M = 25,000 × [0.0054167 × (1.0054167)60] ÷ [(1.0054167)60 − 1] = $489.15 a month. Over the full term that is $29,349.22 paid, of which $4,349.22 is interest.

Frequently asked questions

How is a monthly loan payment calculated?
A standard amortizing loan uses M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1], where P is the amount borrowed, r is the monthly interest rate, and n is the total number of monthly payments. The result is a fixed payment that covers principal and interest for the whole term.
How does the interest portion change over time?
Interest is charged on the remaining balance each month. As the balance falls, the interest portion of a fixed payment falls and the principal portion rises. Interest is not necessarily most of an early payment: it depends on the rate and term. This pattern follows from the formula and is not an extra fee.
How are extra payments treated?
This model applies extra payments to principal after the monthly interest charge. At a positive rate, paying principal earlier reduces later interest. It assumes no prepayment charge or restriction; check your lender terms before making extra payments. The last payment is capped to clear the balance.
Does this calculator include fees, taxes, or insurance?
No. This is the principal-and-interest payment only. Real loans may add origination fees, closing costs, or — for mortgages — property tax and insurance collected through escrow. Check your lender's disclosure for the full monthly cost.
Sources and method
Last reviewed: 19 Sep 2026 Sources last verified: 19 Sep 2026 Results use the assumptions explained on this page. Report an error How we check calculations

Related calculators

Compound Interest Calculator Watch savings grow when interest earns interest, with a year-by-year schedule. 6 inputsOpen → Percentage Calculator Percent of, part-to-whole, percentage change and adjustments. 2 inputsOpen → Mortgage Calculator Principal, interest, taxes, insurance and PMI — the full monthly payment. 9 inputsOpen → Auto Loan Calculator Monthly payment after trade-in and sales tax, plus the full amortization schedule. 7 inputsOpen →