How the Amortization Schedule Is Built
AnyTool Amortization Calculator builds a full month-by-month schedule in the browser using the reducing-balance method. The level payment is the standard EMI, P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), where P is the loan amount, r the monthly rate (annual rate ÷ 12 ÷ 100) and n the number of months. For each row it charges interest on the outstanding balance, repays the rest of the payment as principal, and carries the new balance forward until it reaches zero. Because the balance falls each month, the interest share shrinks and the principal share grows from the first row to the last. The 0% case degrades cleanly to a flat payment of P ÷ n. All arithmetic is pure client-side JavaScript shared through a reusable, unit-tested loan engine.
- Payment = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1); r = annual rate ÷ 12 ÷ 100
- Each row: interest = balance × r, principal = payment − interest
- Balance carries forward until it reaches zero
- Interest share is highest early and falls as the balance reduces
- All math is client-side JavaScript — no server round-trip
