Should You Pay Off Your Mortgage Early? The Real Math in 2026

The Core Question

You have $500/month extra. Should it go toward extra mortgage principal or into your investment account?

This is one of the most genuinely contested personal finance questions because both answers can be correct depending on your numbers and your psychology.

Let's run the actual math.

The Numbers: Extra Payments vs Investing

Scenario: $400,000 mortgage, 6.74% APR, 30-year term. $500/month extra available.

Option A: Extra mortgage payments

• Interest saved: $128,400
• Loan paid off: 9 years and 4 months early
• Guaranteed after-tax return: 6.74% (your mortgage rate)
• Risk level: Zero

Option B: Invest $500/month in index funds instead

• Assumed return: 7.5% (conservative long-run equity estimate)
• Value after 20.7 years (when Option A payoff date): $284,000
• Net gain vs Option A: $284,000 − $128,400 = $155,600 ahead

Option B wins mathematically — but only if you actually invest the $500/month, don't panic-sell during downturns, and sustain it for 20 years.

The Guaranteed Return Argument

Here's why prepayment is more compelling than the numbers suggest:

Your mortgage rate is a risk-free, guaranteed, after-tax return. The stock market's 7.5% historical average comes with the possibility of a 40% drawdown in any given year.

Paying down a 6.74% mortgage is mathematically equivalent to putting money in a savings account that pays 6.74% guaranteed. No HYSA, no CD, no bond offers that. It's only stocks that beat it — and stocks come with risk.

The breakeven calculation:

• If your mortgage rate is above 7%: Prepaying is very likely the better risk-adjusted move
• If your mortgage rate is 5-7%: Personal risk tolerance determines the right call
• If your mortgage rate is below 5%: Invest — the spread to equities is too large to give up

The Tax Variable

Mortgage interest deduction matters only if you itemize deductions. In 2026, the standard deduction is $14,600 (single) / $29,200 (married filing jointly). Most homeowners don't itemize — meaning the mortgage interest deduction provides no actual benefit.

If you do itemize, your effective after-tax mortgage cost is:

• 6.74% × (1 − your marginal tax rate)
• At 24% marginal rate: 6.74% × 0.76 = 5.12% effective rate

At 5.12% effective, the invest-instead argument is much stronger.

The Psychological Dimension

The math ignores something real: the feeling of owning your home outright.

A paid-off home provides:

• Freedom from foreclosure risk regardless of income disruption
• Lower required monthly cash flow (easier to take career risks, work less)
• Psychological security that reduces financial anxiety

These aren't irrational. If you're a business owner, freelancer, or someone with variable income, eliminating your largest fixed monthly obligation has real optionality value.

The behavioral finance case for prepayment: Most people don't actually invest the $500/month if they don't prepay it. Lifestyle creep absorbs it. Forced savings via mortgage prepayment has a 100% execution rate.

When Prepaying Wins Clearly

Prepay your mortgage when:

• Your mortgage rate is above 7%
• You're within 5-10 years of retirement and want reduced fixed costs
• You have variable income and a lower monthly floor matters
• You're fully funding 401k and IRA already
• The debt causes you significant stress

When Investing Wins Clearly

Invest instead when:

• Your mortgage rate is below 5%
• You have not maxed out tax-advantaged accounts (401k, IRA, HSA)
• You have 20+ years until you need the money
• You have stable income and strong risk tolerance
• You have a high marginal tax rate and itemize deductions

The Optimal Order of Operations

Before paying extra on your mortgage, ensure you've done these first:

1. Emergency fund — 3-6 months of expenses in a HYSA
2. Employer 401k match — always take free money first
3. High-rate debt — anything above 8% APR (credit cards, personal loans)
4. Max HSA — triple tax advantage, best account in the tax code
5. Max Roth IRA — $7,000/year, tax-free growth
6. Max 401k — $23,000/year limit in 2026

Only after all of the above does the mortgage prepayment vs. taxable investing decision become relevant.

The Middle Path: Do Both

Split the extra $500/month — $250 to extra principal, $250 to investments. You build equity faster than the standard schedule, maintain market exposure, and reduce the regret risk of going all-in on either option.

Related Tools

• Mortgage Prepayment Savings Calculator — See exactly how much you'd save
• Roth vs HYSA Calculator — Compare after-tax savings options
• Investment Fee Impact Calculator — Understand true investment returns
• Compare Mortgage Rates →