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Extra cash: kill the loan or feed the market?
Your mortgage and the return you expect — the calculator prices both doors.
X VS Y COMPARISON · MONEY · MORTGAGE
Pay Off Mortgage Early vs Invest
You’ve got an extra $500 a month. Two doors: throw it at the mortgage and bank guaranteed interest savings, or invest it and let compounding work. The paydown’s return is your mortgage rate, locked in; the market’s return is a forecast. Enter your balance, rate, and expected return — this calculator runs both doors with your real numbers: months shaved, interest saved, and what the same money grows to invested.
What the comparison shows
A $300,000 balance at 6.75% with 25 years left, and $500 extra a month — a $2,072.73 scheduled payment. Door one, pay down: the loan dies in 191 months instead of 300, saving $130,428 in interest and shaving 109 months (9.1 years) off the term — guaranteed, the day you commit. Door two, invest at 8%: the same $500 a month compounds for 25 years into $475,513 ($325,513 of it pure growth, on $150,000 of contributions). On paper, investing finishes $345,085 ahead — but only if the market actually delivers 8%. The paydown’s 6.75% is a promise; the market’s 8% is a forecast.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Months shaved | original term − payoff term | How much sooner you own the home free and clear: 109 months here. |
| Interest saved | Σ interest baseline − Σ interest accelerated | Guaranteed money back in your pocket: $130,428 here. |
| Investment future value | E × (((1+j)n − 1) ÷ j) | What the extra becomes invested: $475,513 here. |
| Investment growth | future value − contributions | Compounding’s share of the pile: $325,513 here. |
| Dollar gap | investment FV − interest saved | The paper lead for investing: $345,085 here — before risk and taxes. |
Who uses this
- Homeowners with a bonus or raise: the extra cash finally exists — this prices both doors before the money finds a third one.
- Pre-retirees: entering retirement without a mortgage payment is a cash-flow superpower — see exactly what that freedom costs in forgone growth.
- Refinance shoppers: compare the paydown against investing after a refi, when the rate — and the guaranteed return — has changed.
- Conservative investors: if your honest expected return is 5–6%, the mortgage often wins outright — the calculator makes that visible.
Accuracy & limitations
The mortgage side assumes a fixed-rate loan with the extra applied to principal every month and no prepayment penalties (rare on US residential mortgages, but check yours). The investing side assumes a constant annual return compounded monthly — real markets bounce around, and sequence risk means a bad decade early on hurts more than the average suggests. Taxes are not modeled: mortgage interest may be deductible if you itemize (the 2026 standard deduction is $32,200 married filing jointly / $16,100 single, so many homeowners don’t clear the itemizing gate), which lowers the paydown’s effective return; investment gains are taxed too. PMI, escrow, and HOA aren’t in the math. And there’s a liquidity asymmetry the numbers can’t show: invested money is spendable in an emergency; home equity is not. This is a comparison, not financial advice.
Cite this calculatorBright Side Kit. “Pay Off Mortgage Early vs Invest.” brightoolbox.com, 2026.
Bright Side Kit. "Pay Off Mortgage Early vs Invest." https://brightoolbox.com/payoff-mortgage-early-vs-invest/ Accessed October 22, 2026.Frequently asked questions
Is it better to pay off my mortgage early or invest the extra money?
Compare the guaranteed return (your mortgage APR) against your expected investment return. In the $300,000 example above, paying down saves $130,428 guaranteed and kills the loan 9.1 years early; investing at 8% grows to $475,513 on paper — $345,085 more, but only if the market delivers. The honest rule: the paydown wins whenever your expected return is at or below your mortgage rate; above it, you’re being paid to take risk. Run your own numbers above — the gap moves fast with the rate spread.
What investment return do I need to beat paying down my mortgage?
Roughly your after-tax mortgage rate: APR × (1 − your marginal tax rate) if you itemize and deduct the interest — plus a risk premium, because the paydown’s return is certain and the market’s isn’t. At 6.75%% with a 22%% marginal rate and itemizing, the hurdle is about 5.3%%; without itemizing it’s the full 6.75%%. Add 1–2 points for the risk you’re taking, and you get the real hurdle rate.
Should I pay off my mortgage before I retire?
Often yes, for cash-flow reasons: entering retirement with no mortgage payment can cut your required monthly income by a third or more, which also cuts the taxes you pay on withdrawals. But never drain your emergency fund or retirement accounts to do it — liquidity matters more in retirement, not less. The sweet spot is accelerating payments in your last 5–10 working years while keeping 6–12 months of expenses liquid.
What if I have PMI or a high-rate ARM?
Kill PMI first — every extra dollar toward 20%% equity earns an outsized return because it deletes a pure fee, no break-even math needed. An ARM is different from a fixed loan: the paydown’s “guaranteed” return floats with the rate, so the comparison above understates the value of paying down before a reset.
Does paying off my mortgage early hurt my credit score?
No lasting damage. You may see a small temporary dip when the account closes (less credit mix, and installment history stops updating), but a mortgage paid in full and on time is positive history — scores typically recover within a few months. Don’t let the score tail wag the $130,000 dog.