About this tool
Compute the level monthly payment that fully amortizes a fixed-rate loan over its term, along with the total amount paid and total interest.
Formula
M = P · r / (1 − (1 + r)^(−N)) where P=principal, r=monthly rate (APR/12), N=number of months.
Worked example
$250,000 at 6.5% APR for 30 years → M ≈ $1,580.17/month. Total paid ≈ $568,861. Total interest ≈ $318,861.
Notes
This is the most common formula for mortgages and auto loans in the US. The first payment is mostly interest; the last payment is mostly principal.