Mortgage Rate Calculator — Monthly Payment & Total Interest
Enter your loan amount, annual interest rate and loan term to see your monthly repayment, the total interest you will pay, and how your balance shrinks year by year over the life of the loan.
%
years
Fixed monthly repayment covering principal and interest
682,633.47
Total costPrincipal
43.9%
Total interest
56.1%
- 1
Monthly interest rate
r = 6.5% ÷ 12 ÷ 100 = 0.005417 - 2
Number of payments
n = 30 × 12 = 360 - 3
Growth factor
(1 + r)ⁿ = (1 + 0.005417)ⁿ = 6.9918How much one unit of principal grows over the whole term at the monthly rate. - 4
Monthly payment
300,000 × 0.005417 × 6.9918 ÷ (6.9918 − 1) = 1,896.20
How does this calculator work?
Monthly mortgage payment M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount, r is the annual rate divided by 12, and n is the term in months. Multiply by n to get total repaid; subtract P to find total interest. Enter the three inputs to see the full amortisation picture.
Formula
How this is calculated
A fixed-rate mortgage charges the same nominal interest rate for every month of the loan. Each monthly payment covers two components: the interest that accrued on the outstanding balance during that month, plus a slice of the original principal. Early payments are almost entirely interest; later ones are mostly principal — a pattern called amortisation.
The standard amortisation formula M = P × [r(1+r)^n] / [(1+r)^n − 1] ensures that exactly n equal payments of M will retire the loan. As r (the monthly rate = annual rate / 12) or n (total months = years × 12) change, the monthly payment and total interest change dramatically. Doubling the term roughly doubles the total interest paid, even if the monthly payment falls.
This calculator models a pure principal-and-interest loan. Property taxes, homeowners insurance, private mortgage insurance (PMI) and escrow are not included, and can add a significant amount to the real monthly cost. It also assumes no prepayments — making extra principal payments each month reduces the balance faster and cuts total interest substantially.
Frequently asked questions
A 1% increase in rate on a $300,000 30-year loan adds roughly $170 to the monthly payment and about $60,000 to the total interest paid. The higher the balance and the longer the term, the larger the impact of even a small rate change.
A 15-year mortgage has a higher monthly payment (often 30–50% more than a 30-year) but typically carries a lower rate and charges 40–55% less total interest. A 30-year loan reduces the monthly burden but significantly increases the overall cost of the loan.
Property taxes, homeowners insurance, PMI (for loans above 80% LTV), HOA fees and escrow are excluded. These can raise your real monthly housing cost by 20–50% above the principal-and-interest payment alone.
Also known as
TG we-Calculate Editorial Team. (2026). Mortgage Rate Calculator — Monthly Payment & Total Interest [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/mortgage-rate-calculator
TG we-Calculate Editorial Team. "Mortgage Rate Calculator — Monthly Payment & Total Interest." TG we-Calculate. 2026. https://we-calculate.com/calculator/mortgage-rate-calculator.
TG we-Calculate Editorial Team, "Mortgage Rate Calculator — Monthly Payment & Total Interest," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/mortgage-rate-calculator
@misc{wecalculate_mortgage_rate_calculator, title = {Mortgage Rate Calculator — Monthly Payment & Total Interest}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/mortgage-rate-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?