Should You Pay Extra on Your Mortgage or Invest?

The Short Answer

If your mortgage rate is under 5%, investing usually wins mathematically. If your rate is over 6%, paying down the mortgage is often the better return. Between 5-6%, it depends on your risk tolerance and timeline.

$500/month over 15 years: investing at 7% outpaces mortgage interest savings

The Math: $500/Month for 10 Years

On a $300,000 mortgage at 6%:

• Pay extra: Save ~$52,000 in interest, pay off 3.5 years early
• Invest at 7%: Grow to ~$86,000 (but mortgage still has 10 years left)

The Math: $500/Month for 15 Years

Same mortgage, longer timeline:

• Pay extra: Save ~$82,000 in interest, pay off 6 years early
• Invest at 7%: Grow to ~$155,000 (mortgage paid off anyway)

The gap widens with time. Over 15 years, investing wins by roughly $73,000. But that assumes consistent 7% returns — which is not guaranteed.

When Paying the Mortgage Wins

• High mortgage rate (over 6%): The guaranteed return beats average market returns after taxes
• Risk-averse: You sleep better with no debt
• Near retirement: Eliminating a fixed expense reduces sequence-of-returns risk
• No emergency fund: Build 3-6 months cash first

When Investing Wins

• Low mortgage rate (under 5%): Historical market returns (7-10%) beat your interest cost
• Long time horizon (over 15 years): More time for compounding
• Tax-advantaged accounts: 401(k) match + Roth IRA space is use-it-or-lose-it
• Liquidity: Investments can be sold; home equity requires refinancing or selling

The Tax Angle Most People Miss

Mortgage interest is tax-deductible for many homeowners, which effectively lowers your rate:

• 6% mortgage, 24% tax bracket: Effective rate = 4.56%
• 6% mortgage, 32% tax bracket: Effective rate = 4.08%
• Standard deduction taker: You get no mortgage interest benefit — use the full rate

If your effective mortgage rate drops below 5%, the math strongly favors investing.

The Hybrid Approach

Many financial planners recommend splitting extra cash: half to mortgage, half to investments. This gives you guaranteed progress on debt while still capturing market returns. Adjust the split based on your rate — higher rate = more toward mortgage.