Mortgage Prepayment Calculator

Calculate how a one-time lump-sum prepayment reduces total interest and shortens the remaining mortgage term.

Finance planning estimate

Topic review: James Whitfield

Retired Financial Planner. Assigned as the finance topic reviewer for mortgage, retirement, annuity, pension, and long-term planning calculators.

Reviewed 27 March 2026 Updated 27 March 2026 View reviewer profile Contact editorial team

Original loan Interest rate (%) Loan term (years) Current month Lump sum prepayment

Display currency

Currency

Interest saved

$59,962.73

A $20,000.00 lump sum at month 60 saves 44 months.

Balance at month 60: $279,163.07
After lump sum: $259,163.07
Monthly payment: $1,798.65
Months saved: 44

About this calculator

Finance planning estimate Reviewed 27 March 2026 Updated 27 March 2026

Topic review

James Whitfield

Retired Financial Planner. Assigned as the finance topic reviewer for mortgage, retirement, annuity, pension, and long-term planning calculators.

Formula provenance

The methodology summary explains the formula family in use, and the source list points to the primary or authoritative references checked for this topic.

Methodology

Uses standard fixed-rate amortisation math to translate the balance, rate, term, and any recurring housing-cost inputs in Mortgage Prepayment into payment, payoff, or affordability estimates.

Limitations

Assumes the rate and fee structure entered stay constant unless the tool explicitly models changes.
Does not replace a lender's underwriting, insurance, escrow, or affordability assessment.
Taxes, insurance, and housing costs vary by property and jurisdiction.

Disclaimer

This is a planning estimate, not a mortgage offer. Confirm rates, fees, insurance, taxes, and lending eligibility with your lender or an independent financial adviser before making a property decision.

Primary finance sources

CFPB mortgages — Official consumer guidance on mortgage costs, comparisons, and borrowing decisions.

Change notes

Finance change note: the formula, tax or rate assumptions, source set, disclaimer, and planning guidance for this calculator were last reviewed on 2026-03-27. Report a correction at calcipedia@proton.me; substantive rule or assumption changes refresh both the reviewed date and the updated date shown on the page.

See our calculation methodology and editorial standards, plus the editorial contact route, for how this estimate is produced and corrected.

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