№ 007 · Mortgage cluster
Mortgage Payoff vs Invest Calculator
You have spare money each month — should it go toward killing the mortgage early, or into the market? This runs both plays over the same horizon with the same budget, ends them both with the house paid off, and shows which one leaves you richer. Spoiler: it usually comes down to your return versus your rate.
Same budget · net-worth crossover
Just sizing the impact of extra payments? See the Loan Payoff Calculator. Projecting the investing side on its own? The Investment Growth Calculator.
Your mortgage01
$
%
The money in play02
$
%
After 30 years · same budget either way
Investing wins
$49,527.54 more at payoffPrepaying saves $119,700.76 interest, 108 mo early
Pay it down
Portfolio at payoff$316,462.50
mortgage gone in 21 yr
then invest the freed payment
then invest the freed payment
Invest the differenceWins
Portfolio at payoff$365,990.04
pay the mortgage on schedule
invest the extra from day one
invest the extra from day one
- Pay it down
- Invest the difference
| Start | Pay it down -$300,000.00, Invest the difference -$300,000.00 |
|---|---|
| Year 2.9 | Pay it down -$277,164.21, Invest the difference -$276,996.53 |
| Year 5.9 | Pay it down -$249,124.23, Invest the difference -$248,324.56 |
| Year 9.0 | Pay it down -$214,548.53, Invest the difference -$212,412.92 |
| Year 12.0 | Pay it down -$174,193.27, Invest the difference -$169,830.02 |
| Year 15.1 | Pay it down -$124,431.77, Invest the difference -$116,470.52 |
| Year 18.1 | Pay it down -$66,352.30, Invest the difference -$53,169.61 |
| Year 21.1 | Pay it down $3,151.13, Invest the difference $23,825.51 |
| Year 24.2 | Pay it down $90,294.56, Invest the difference $120,371.46 |
| Year 27.2 | Pay it down $195,125.78, Invest the difference $234,982.37 |
| Year 30.0 | Pay it down $316,462.50, Invest the difference $365,990.04 |
Both paths spend the same total each month and end with the house paid off at year 30; the line that’s higher has more money left over. Investing tends to win when your return beats the mortgage rate — but it carries market risk and debt that paying down does not.
How it works · methodology
The math, in the open.
Both paths spend (scheduled P&I + extra) every month for the original term.
Prepay: extra → mortgage until it clears, then invest the whole payment.
Invest: pay the mortgage on schedule, invest the extra from month 1.
Winner = the larger side portfolio at the original payoff month
(the house is paid off either way).- balance
- Remaining mortgage principal
- rate
- Mortgage APR
- extra
- Spare dollars per month — prepay it or invest it
- return
- Expected annual investment return
Assumptions & limits
- Both strategies use the identical monthly budget and the same horizon (the original payoff date).
- Pre-tax throughout — it does not model investment taxes or a mortgage-interest deduction.
- The investment return is a steady assumption; real markets vary and can fall sharply.
- Prepaying is a guaranteed return equal to the mortgage rate; investing is not guaranteed.
By the MintNumber Editorial Team·Reviewed
Frequently asked
Questions about payoff vs investing
Should I pay off my mortgage early or invest the extra?
It comes down to a single comparison: your expected after-tax investment return versus your mortgage rate. If your investments reliably earn more than the mortgage costs, investing the extra builds more wealth; if not, prepaying wins by guaranteeing a return equal to your mortgage rate. This calculator runs both paths over the same horizon with the same monthly budget so you can see the gap in dollars — but the math is only half the decision; risk tolerance and peace of mind matter too.
How does the calculator keep the comparison fair?
Both paths spend exactly the same amount every month — your scheduled payment plus the extra — and both finish at the same point in time with the house fully paid off. On the prepay path the extra knocks the mortgage out early, and from then on the entire freed-up payment is invested. On the invest path you pay the mortgage on its normal schedule and invest the extra from the very first month. Because the house is paid off either way at the end, the only thing left to compare is the size of the side investment account.
Why does paying down the mortgage guarantee a return?
Every extra dollar of principal you pay is a dollar that stops accruing interest at your mortgage rate for the rest of the loan. Prepaying a 6% mortgage is therefore a risk-free 6% return on that money — guaranteed, and not subject to the market. That is the bar investing has to clear: to come out ahead, your investments must beat the mortgage rate after taxes and fees, and do it reliably, not just on average.
Does this account for taxes or the mortgage interest deduction?
Not directly — it compares pre-tax mortgage interest against a pre-tax investment return. Two tax effects can shift the real answer: investment gains may be taxed (lowering the effective return), and mortgage interest may be deductible if you itemize (lowering the effective mortgage rate). Most households since 2018 take the standard deduction and get no mortgage-interest benefit, but if both apply to you, nudge the investment return down and the mortgage rate down to approximate the after-tax picture.
What about risk and peace of mind?
The calculator shows expected dollars, but a paid-off house is certain while investment returns are not. Prepaying lowers your monthly obligations and is immune to market crashes; investing keeps your money liquid and historically grows faster, but can fall sharply right when you need it. Many people split the difference — invest enough to capture long-run growth while still making some extra principal payments for the security. There is no single right answer, only the one that lets you sleep.
How is this different from the loan payoff calculator?
The loan payoff calculator answers one side of this question — how much faster and cheaper extra payments make the loan. This calculator pits that prepay strategy against the alternative of investing the same money, and tells you which leaves you wealthier. Use loan payoff to size the impact of extra payments; use this when you are deciding whether to make them at all.