By the CalcLedger editorial team · Updated September 2026 · Examples use illustrative rates · How we calculate
If you have extra money each month, there are two popular places to put it: extra payments on your mortgage, or investments such as an index fund or a retirement account. Both build wealth. The best answer depends on your mortgage rate, your other financial priorities, and how much you value certainty.
First, the non-negotiables
Before comparing mortgage prepayment with investing, most financial planners suggest taking care of these first:
- An emergency fund of three to six months of expenses. Money you put into your house is hard to get back quickly.
- Your full employer 401(k) match, if you have one. A match is an instant 50% or 100% return that nothing else can beat.
- High-interest debt, such as credit cards. Paying off a 22% card is a far better return than prepaying a mortgage. See avalanche vs. snowball.
After those, the question gets interesting.
The core comparison
Every extra dollar you pay on your mortgage earns a guaranteed return equal to your mortgage rate, because it saves you that interest. Every dollar you invest earns whatever the market returns, which is uncertain but historically higher than typical mortgage rates over long periods.
- Mortgage rate clearly below the return you expect from investing: investing usually comes out ahead in the long run.
- Mortgage rate close to or above expected returns: prepaying the mortgage is competitive, with no risk.
Example: $300 a month extra on a $300,000 mortgage at 6.5%
The regular payment on a $300,000, 30-year loan at 6.5% is about $1,896. Adding $300 a month:
- Pays the loan off in about 250 months, roughly 20 years and 10 months, instead of 30 years.
- Saves about $135,000 in interest.
Now compare two plans over the full 30 years:
| Plan | Wealth in investments after 30 yrs (7% return) |
|---|---|
| A: pay $300 extra, then invest the whole $2,196 once the house is paid off | ≈ $337,000 |
| B: pay the regular mortgage, invest $300 a month from day one | ≈ $366,000 |
Both plans end with a paid-off house after 30 years. Plan B comes out about $29,000 ahead, assuming a steady 7% return. If investments earned the same 6.5% as the mortgage rate, the two plans end up roughly equal. If returns were lower, Plan A would win. At a 6.5% mortgage rate, the math is close, and the guaranteed return of prepaying is attractive.
Investments after 30 years: prepay first or invest from day one?
$300 a month extra, 6.5% mortgage, 7% assumed investment return
Same example with a 3% mortgage
Many homeowners locked in rates around 3% before 2022. On a $300,000 loan at 3%, the regular payment is about $1,265. Paying $300 extra saves about $46,000 in interest. But in the same 30-year comparison at a 7% return, Plan A ends with about $206,000 invested, while Plan B ends with about $366,000. With a low-rate mortgage, investing wins by a wide margin, and prepaying that loan is one of the lowest-return uses of extra cash.
Reasons to prepay anyway
- Guaranteed return. Investment returns vary a lot. A 7% average includes years with big losses.
- Lower fixed costs in retirement. Entering retirement without a mortgage payment reduces how much income you need.
- Peace of mind. For many people, owning their home outright has value that doesn't show up in a spreadsheet.
- You wouldn't actually invest the difference. Plan B only works if the money really gets invested every month for decades.
Reasons to invest instead
- Liquidity. Invested money can be sold if you need it. Money paid into your house can only be reached by selling or borrowing against it.
- Tax-advantaged accounts. Contributions to a 401(k) or IRA may lower your taxes now or grow tax-free, which widens the advantage of investing.
- Inflation. A fixed mortgage payment gets easier to afford over time as incomes and prices rise.
- A low mortgage rate, as the 3% example shows.
Lump sums and mortgage recasting
If you get a bonus, an inheritance, or proceeds from selling another property, ask your lender about a recast. You make a large principal payment, and the lender recalculates your monthly payment over the remaining term. Unlike refinancing, your rate doesn't change, and the fee is usually a few hundred dollars instead of thousands in closing costs. It's a way to prepay while also lowering your required payment, which gives you more flexibility. Not all loans allow it: FHA and VA loans generally don't.
A middle path
You don't have to choose one. Many people split extra money, for example half to investments and half to the mortgage. Others invest while the mortgage rate is low and switch to prepaying if they refinance at a higher rate, or as retirement gets closer. If you do prepay, make sure the extra goes to principal, and check that your loan has no prepayment penalty. Most don't.
If you have private mortgage insurance, prepaying until you reach 80% loan-to-value can be especially valuable, because removing PMI is an extra return on top of the interest saved. See our PMI guide.
Run your own numbers
Use the mortgage calculator to see your loan's interest cost, and the compound interest calculator to project what a monthly investment could grow to. Try a conservative return as well as an optimistic one. If the result still favors investing at a cautious return, investing is probably the better choice for you.