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Interest Rate Calculator

Adjust the inputs below. Results update as you type.

How it works

Given PV, PMT, and n, solve for r using Newton-Raphson iteration (no closed form exists). For simple interest: r = I / (P × t). APY = (1 + APR/n)^n − 1. When comparing credit cards, always use APR (or APY for savings). A difference of 1% on a $300,000 30-year mortgage changes total interest by over $60,000.

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