How the Loan Calculator With Extra Payments works
This calculator builds two full amortization schedules side by side: one using only your regular monthly payment, and one that adds a fixed extra amount to every single payment for the life of the loan. Because that extra money goes straight to principal, the balance shrinks faster, which means less interest accrues every month after that — a compounding effect that grows the longer the loan runs.
The table below shows the exact schedule for the loan with extra payments included, so you can see the payment, principal, interest, and remaining balance for every single month until it's paid off.
Because the payment is larger than required, the loan pays off before its original term ends — that's the "time saved" shown above. Try adjusting the extra payment amount to see how even a small, consistent increase changes your total interest.
A worked example
A $25,000 loan at 6.5% over 5 years has a scheduled payment of $489.15 and costs $4,349.22 in interest. Add $150 to every payment and the loan clears in 45 months instead of 60, with interest cut to $3,170.26.
| Monthly outlay | Payoff | Total interest | |
|---|---|---|---|
| Scheduled | $489.15 | 60 months | $4,349.22 |
| +$150/month | $639.15 | 45 months | $3,170.26 |
| Result | — | 15 months sooner | $1,178.96 saved |
How to read your schedule
The schedule rebuilds itself with the extra amount added to every month's principal. Watch the balance column fall faster than the standard schedule and the payoff month move earlier. The interest saved figure is the whole point.
When to use this calculator
Use it when you can commit to a recurring extra amount — not a one-time payment — and want to see the full effect over the life of the loan. It answers “if I round my payment up to the next $50, when am I done and how much do I save?”
Common mistakes to avoid
- Committing to an extra you cannot sustain. A smaller extra you always pay beats a large one you abandon after three months.
- Not confirming principal-only application. Set it up with the servicer so overpayments reduce the balance every month automatically.
- Prepaying instead of building an emergency fund. Liquidity first, then acceleration.