Mortgage prepayment calculator
See how extra monthly payments and an immediate lump sum could change your interest costs and payoff time.
Your numbers
Your result
Example scenarioProjected interest savings
Compared with your original schedule, assuming the rate stays unchanged
Try a different scenario
See the original schedule alongside your extra-payment plan.
Or save these inputs, change a number and compare with your saved scenario.
Why this number?
The regular monthly payment is first calculated using your current balance and remaining amortization. The lump sum then reduces the opening balance without reducing that regular payment. The extra amount is paid each month on top of the regular payment. The final payment is capped at the remaining balance plus that period's interest.
Result breakdown, line by line
Values use the assumptions above and the exact inputs entered. Compare scenarios before making a decision.
Planning estimate. Rate and return assumptions can change the result.
How is this calculated?Money Figures · Mortgage prepayment calculator · Model v0.1.6 · Values in Canadian dollars
Charts, amortization & comparisonsTake a closer look at your result.
Your projection
SHOWING OUR WORK
Assumptions & methodology
How extra payments work
The regular monthly payment is first calculated using your current balance and remaining amortization. The lump sum then reduces the opening balance without reducing that regular payment. The extra amount is paid each month on top of the regular payment. The final payment is capped at the remaining balance plus that period's interest.
Interest calculation
Semi-annual compounding is converted to a monthly rate: i = (1 + r/2)^(1/6) − 1. Monthly interest = opening balance × i. Interest savings compare the two complete payoff schedules. Calculations retain full precision internally.
Contract limits matter
The model assumes all extra payments are permitted and the rate stays unchanged until payoff. It does not estimate prepayment penalties or annual prepayment privileges. Confirm your mortgage contract's limits, allowed dates and fees before making extra payments.
A worked example
For a C$400,000 balance at 4.50% with 20 years remaining, compare the original schedule with an extra C$250 each month and a C$10,000 lump sum today.
Understand the result
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Compare monthly, regular biweekly and accelerated biweekly payments, including the extra annual commitment and constant-rate assumptions.
Read guideImportant: planning estimate, not financial advice
Money Figures provides general calculator estimates based on the inputs and assumptions shown. It does not consider your full financial circumstances and is not financial, tax, investment, lending or legal advice. Results do not guarantee lender, insurer, government or tax treatment. Confirm material decisions with the relevant institution or an appropriately qualified professional.
Your next money decision
Confirm your prepayment privileges
Before increasing payments or paying a lump sum, check the terms of your own mortgage contract, including any penalty or annual limit.
Explore the next tool or guide →Sources
Sources checked: 2026-10-09. Targeted technical check: 2026-10-11. Financial model v0.1.6; release v0.2.9. Independent financial review is pending. Calculation standards · Change history.