About this calculator
Estimate payoff time and interest for a fixed monthly payment.
This simplified model assumes a constant rate and payment and no new charges or fees.
Formula
Each month: interest = balance × annual rate ÷ 12; new balance = balance + interest − payment.
Example
A larger payment generally reduces both payoff time and total interest.
Accuracy
NUMTX shows the assumptions next to the calculation so you can replace defaults with values that match your situation. For measurements, supplier rates, fees, interest, tax or regulated work, confirm important figures with the appropriate official or professional source.