Interactive mortgage payoff accelerator

Mortgage Payoff & Investment Fund Calculator

Compare putting extra cash directly toward principal with investing it in a separate payoff fund. Adjust the assumptions to see the estimated crossover points.

Estimated regular monthly principal & interest payment-
Standard payoff--
With extra principal--
With investment fund--
Investment fund result-

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Investment income milestones

Projected fund income is compared with the regular mortgage payment.

Income covers monthly interest--
Virtual mortgage payoff--

A virtual mortgage payoff is a cash-flow milestone, not a loan payoff. The annual investment-return assumption is divided by 12 to estimate monthly growth; it does not mean the fund distributes that amount as cash. The mortgage balance remains outstanding unless you use funds to pay it off.

Estimated payoff paths

Mortgage balance / payoff gap / fund value
Standard mortgage balanceExtra principal balanceInvestment fund payoff gapProjected investment fund

The green dashed line shows the projected fund growing from its current balance with monthly contributions. Its labeled endpoint marks the projected month the fund fully pays off the mortgage. The gold payoff gap is the remaining mortgage balance less that fund.

Estimated comparison

The same additional monthly cash is allocated differently in each alternative: directly to mortgage principal or to the investment fund.

Payoff pathPayoff timingTime to payoffTotal mortgage interestTime vs. standard
Standard mortgage balance---Baseline
Extra principal payoff----
Investment payoff----

How the comparison works

Choice 1 - pay down principal: the current investment balance is modeled as a one-time principal payment today, and the additional monthly cash is then applied directly to the mortgage. The return is the mortgage interest you avoid, which is effectively guaranteed if the mortgage terms remain unchanged.

Choice 2 - invest the difference: the current investment balance remains invested while the regular mortgage payment continues. The same additional cash is invested monthly. When the projected fund reaches the remaining mortgage balance, the model uses it to pay off the loan. Its outcome depends on the assumed return and is not guaranteed.

Important: this calculator models only non-negative assumed returns. Actual investment values can decline, and taxes, fees, withdrawal timing, or loan prepayment rules can change the result. Confirm your lender's terms and consider a qualified adviser before acting.

Educational estimate only - not investment, tax, or lending advice; not a loan payoff statement. Assumes a fixed interest rate, monthly compounding, on-time payments, and no escrow, fees, tax effects, investment fees, or prepayment penalties.