Free Mortgage Calculator - Calculate Monthly Payments & Total Interest
Calculate your monthly mortgage payments.
Formula & Methodology
The Mortgage Calculator converts your annual interest rate to a monthly rate and uses the loan amount, that monthly rate, and the number of monthly payments to find the fixed payment that pays the loan to zero. Total interest is the sum of all those payments minus the original principal.
- M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1]
- Total Interest = (M × n) − P
Worked Example
Using the Mortgage Calculator: apply the formula above to your input values. For instance, M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1], then Total Interest = (M × n) − P. The tool performs each step instantly and shows the result.
Frequently Asked Questions
What is included in my mortgage payment?
The core payment covers principal and interest; full PITI also adds property taxes and homeowners insurance.
How does the interest rate affect my payment?
Even a small rate change noticeably shifts the monthly payment and adds up to large differences over 30 years.
Should I choose a 15- or 30-year mortgage?
A 15-year loan has higher payments but far less total interest, while a 30-year loan lowers monthly cost.