Example 1 — Small recurring extra
- Principal: 200,000
- 6%, 20 years
- +500/mo.
≈ 93 mo. sooner
Interest − ≈ 61,565
A steady extra shortens a 20-year loan a lot.
Loan overpayment calculator
Enter the remaining balance and an extra payment — we'll show how many months you shave off and how much interest stays in your pocket. Recurring extra or a one-time lump; we can do both.
Quick estimate: extras go to principal, and we compare one baseline with one overpayment scenario (monthly + lump combined). Lender rules and fees vary — for the full month-by-month table, open the Amortization schedule.
Result
Enter your numbers and hit Calculate — the result shows up right away.
How results are calculated
Baseline = amortizing (or your) payment with no extras for the remaining term.
With overpayment = same payment + monthly extra; lump reduces principal on the chosen payment number. Surpluses go to principal.
Shorten term keeps the instalment. Reduce payment recalculates after the lump for the same remaining term (simplified model).
Net interest saved = gross − fee (when entered).
How to use the calculator
- Enter remaining principal, rate, and term.
- Add a monthly extra (main field).
- Under Additional options: bank payment, lump + payment #, start date, fee, shorten/reduce mode.
- Compare time and interest — open the Amortization schedule for the full table.
Usage examples
Example 2 — Lump sum only
- Principal: 150,000
- 7.5%, 15 years
- Lump: 20,000
≈ 38 mo. sooner
Interest − ≈ 34,082
A one-time payment cuts principal immediately.
Example 3 — Combined + fee
- Principal: 80,000 · +200/mo. + 5,000
- Fee 200 · start date
≈ 36 mo. sooner
Interest − ≈ 15,396 (net of fee)
Both extras in one scenario; payoff date shown.
Which tool to use for overpaying and repaying debt
- Loan overpayment – fastest way to see how much interest and how many months you save by paying extra into an existing loan.
- Repayment schedule – full month-by-month table with instalments, balance and any extra payments; useful when you need the entire path, not just a summary.
- Debt repayment – for a single debt balance and a fixed monthly payment, when you want to know how many months it will take to reach zero.
If you only need a quick answer to “is overpaying worth it?”, start here. When you need a full schedule or a payoff horizon at a fixed payment, go to the repayment schedule or debt-repayment calculator instead.
FAQ
How do loan overpayments work?
Extra money covers interest first, then knocks down principal. Lower balance = less interest later. We compare a no-extra schedule with one overpayment scenario.
Why do earlier extras matter more?
The sooner you cut principal, the longer interest runs on a smaller balance. The same lump sum early usually saves more than late in the term.
Shorten the term or reduce the payment?
Shorten (default) keeps the instalment and finishes earlier. Reduce recalculates the payment after a lump for the same remaining term — a simplified sketch; lenders may do it differently.
Do lenders charge a prepayment fee?
Depends on your contract and timing. Plug a flat fee under Additional options to see gross vs net interest saved after that fee.
How is this different from the full amortization schedule?
Here you get the short version: time saved, interest, extras paid. The full month-by-month table, CSV, and richer variants live in the Amortization schedule calculator.
Can I combine a monthly extra and a lump sum?
Yes — both go into one scenario. No separate A/B variants.
Where does the currency come from?
From the page header — same currency as the rest of Calcboxer. Switch it there if you need another one.