Mortgage Prepayment Comparison Calculator
Compare three mortgage prepayment strategies — extra every month, extra once a year, or a one-time lump sum — by interest saved and payoff time.
Your inputs
Results
Largest interest saving
Extra monthly
- Extra monthly — interest saved
- $91,173.87
- Extra yearly — interest saved
- $87,882.99
- Lump sum — interest saved
- $83,702.12
- Extra monthly — payoff months
- 279
- Extra yearly — payoff months
- 281
- Lump sum — payoff months
- 303
✓Exact calculation — rounded only for display
| Strategy | Payoff (months) | Total interest | Saved |
|---|---|---|---|
| No prepayment | 360 | $347,515.44 | $0.00 |
| Extra monthly | 279 | $256,341.57 | $91,173.87 |
| Extra yearly | 281 | $259,632.45 | $87,882.99 |
| One-time lump sum | 303 | $263,813.32 | $83,702.12 |
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What this calculator does
There are several ways to pay a mortgage off early. This tool runs each strategy against the same loan so you can see which saves the most for the money you have.
Formula and method
Worked example
Calculated by this tool with its default inputs:
Inputs
- Loan amount: 300000 (any currency)
- Interest rate: 6 %
- Term: 30 years
- Strategy 1: extra each month: 200 (any currency)
- Strategy 2: extra once a year (each 12th payment): 2400 (any currency)
- Strategy 3: one-time lump sum with the first payment: 20000 (any currency)
Results
- Largest interest saving: Extra monthly
- Extra monthly — interest saved: 91,173.87
- Extra yearly — interest saved: 87,882.99
- Lump sum — interest saved: 83,702.12
- Extra monthly — payoff months: 279
- Extra yearly — payoff months: 281
How to read the results
Earlier prepayments save more interest because they reduce the balance for longer.
Assumptions and limitations
- Make sure your lender applies prepayments to principal and check for penalties.
Financial results are estimates based on the inputs and assumptions shown. They are not financial advice; confirm figures with your lender, provider or a qualified adviser before making decisions.
Questions
Why does the lump sum save less here?
It depends on the amounts: a 20,000 lump sum now is less money than 200 extra every month for many years.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 2 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Because this calculator can involve personal financial or health details, your inputs are never added to share links or saved to history. Privacy policy