Stop guessing what extra payments actually save you.
Mortgage, car loan, student loan, business loan — same math. We show the amortization schedule, the total interest, and exactly how many years and dollars an extra monthly payment cuts off.
Built and reviewed by Stephen Omukoko Okoth
Mathematical Economist · ex-Morgan Stanley FI · Equilar
Inputs
The loan
Verdict
Add an extra payment to see the impact.
Loans run their full term without extra payments.
The base monthly is your contractual minimum. Anything extra goes straight to principal — and every dollar of principal you knock off saves you the future interest that principal would have generated.
Result
The numbers
Required monthly payment
$ 1,060
Total monthly with extra
$ 1,060
Total interest (no extra)
$ 168.1K
Total interest (with extra)
$ 168.1K
Payoff (no extra)
25 years
Payoff (with extra)
25 years
Trajectory
Balance over time
Common questions
How is the monthly payment calculated?
It's the standard amortization formula: P × r / (1 − (1 + r)^−n), where P is the principal, r is the monthly rate, and n is the number of months. Every payment splits between interest (computed on the current balance) and principal.
What does 'extra monthly payment' really do?
Every dollar of extra payment goes straight to principal, so next month's interest is lower. The savings compound — even a small extra payment can chop years off a 25-year loan.
Does this work for any kind of loan?
Yes — mortgages, car loans, personal loans, student loans, business loans. As long as it has a fixed rate and regular payments, the math is identical.
What is the canonical break-even between extra payments and investing?
If your guaranteed loan rate is higher than your expected after-tax investment return, extra payments win on a risk-adjusted basis. The calculator above shows the savings; compare against your investing alternative explicitly.