Home Loan Extra Payments Calculator
This calculator models how recurring extra payments or a single one‑time extra payment change the time to pay off a mortgage and the total interest paid. It supports monthly, bi‑weekly, and weekly payment schedules and compares results against a no‑extra baseline.
The tool provides estimates only and assumes a fixed interest rate and that extra payments are applied fully to principal on the same schedule as the regular payment. It does not account for prepayment penalties, escrow changes, variable rates, or lender processing rules.
Estimate payoff time and interest when you make a recurring extra principal payment each scheduled payment (works for monthly, bi‑weekly, weekly frequencies).
Inputs
Advanced inputs
Recurring extra settings
One-time extra settings
Results
Scheduled regular payment
-$0.52
Total payment per scheduled period (incl. extra)
$49.48
Estimated payoff time (years)
—
Total interest paid (with extra)
—
Estimated interest saved
—
Estimated months saved
—
| Output | Value | Unit |
|---|---|---|
| Scheduled regular payment | -$0.52 | currency |
| Total payment per scheduled period (incl. extra) | $49.48 | currency |
| Estimated payoff time (years) | — | years |
| Total interest paid (with extra) | — | currency |
| Estimated interest saved | — | currency |
| Estimated months saved | — | months |
Visualization
Methodology
All scheduled payment calculations use standard amortization formulas for fixed‑rate loans with periodic interest r = APR / payments_per_year and scheduled payment computed by the annuity formula.
When recurring extras are present, the calculator treats the extra as an additional principal payment each scheduled period and solves for the number of periods required to reduce balance to zero. For a one‑time extra, it computes the remaining balance immediately before the extra, reduces principal by the extra amount, and then solves for remaining periods.
Results are numeric estimates and are produced using common mathematical functions (exponentials and logarithms). Natural logarithms are used when solving for number of periods. Calculations follow recognized numerical practices for stability but are not a substitute for lender amortization schedules.
Worked examples
Example: $300,000 loan, 3.5% APR, 30 years, bi‑weekly (26) schedule, $50 extra every payment → shows reduced payoff time and interest saved versus baseline.
Example: $200,000 loan, 4.0% APR, 15 years, monthly schedule, $5,000 one‑time extra at payment 12 → computes new payoff date and interest savings.
Further resources
Expert Q&A
Are these results exact for my loan?
These are mathematical estimates based on the inputs and standard amortization formulas. Actual results can differ because lenders may apply extra payments according to loan terms, have minimums, or charge prepayment fees. Always confirm with your lender for legally binding payoff figures.
Does bi‑weekly mean two half‑monthly payments?
Bi‑weekly (26 payments per year) is not the same as twice monthly (24 payments per year). This calculator treats bi‑weekly as 26 equal scheduled payments per year.
Will this account for adjustable rates or escrow changes?
No. The calculator assumes a fixed interest rate for the remaining life of the loan. For adjustable-rate mortgages or loans with escrow changes, results are only illustrative.
What about rounding and numerical limits?
Calculations use standard floating‑point arithmetic. Very small interest rates or extremely high frequencies can produce rounding effects. For critical financial decisions, consult a licensed professional and request an official payoff statement from your lender.
Sources & citations
- NIST - Numerical Methods & Guidance — https://www.nist.gov
- ISO - Financial services standards — https://www.iso.org
- IEEE - Recommended practices for numerical computation — https://www.ieee.org
- OSHA - Safety and operational considerations (contextual guidance) — https://www.osha.gov