Loan Repayment Engine
Analyze your monthly obligations and the total cost of capital for mortgages, personal financing, or auto loans.
Financing Parameters
How the Loan Payment Calculator Works
This calculator computes the fixed monthly payment (principal plus interest) required to fully repay a loan over a set term — the same amortization method lenders use for mortgages, auto loans, and personal loans.
Formula
M = P × [i(1+i)^n] / [(1+i)^n − 1]- M — fixed monthly payment
- P — loan principal
- i — monthly interest rate (annual rate ÷ 12)
- n — total number of monthly payments (years × 12)
Because the payment is fixed but the balance declines each month, the split between interest and principal shifts over the life of the loan: early payments are mostly interest, later payments are mostly principal, even though the total payment never changes.
Total interest paid over the loan's life is simply the sum of all monthly payments minus the original principal — for long terms at meaningful interest rates, this can add up to more than the amount originally borrowed.
Worked Example: $300,000 loan at 6.5% over 30 years
- P = $300,000, i = 0.065/12 ≈ 0.005417, n = 360
- (1+i)^n ≈ 6.992
- M = 300,000 × (0.005417 × 6.992) / (6.992 − 1)
Monthly payment ≈ $1,897 — totaling roughly $682,900 repaid, of which about $382,900 is interest.
Frequently Asked Questions
Does this include property taxes or insurance?
No — this calculates only principal and interest on the loan itself. For a mortgage, actual monthly housing cost is typically higher once property taxes, homeowners insurance, and any HOA or PMI fees are added.
Why does a small rate difference matter so much on a 30-year loan?
Interest compounds against you on the outstanding balance every month for the full term, so even a fraction of a percentage point changes the monthly payment and, over 360 payments, can shift total interest paid by tens of thousands of dollars.