15 vs 30 Year Mortgage: The $300,000 Decision
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The raw comparison
A $400,000 loan, with the 15-year rate about 0.6 points lower as is typical:
| 30-year at 6.5% | 15-year at 5.9% | |
|---|---|---|
| Monthly payment (P&I) | $2,528 | $3,349 |
| Difference | — | +$821/mo |
| Total interest | $510,178 | $202,782 |
| Interest saved | — | $307,396 |
| Paid off in | 2056 | 2041 |
Check your own figures in the mortgage calculator — a small rate difference moves these numbers considerably.
The case for 15 years
- You save roughly $300,000 on this example. That is not a rounding difference; it is a house deposit for a child.
- Lower rate. Lenders price 15-year loans 0.5–0.75 points cheaper because their risk window is half as long.
- Equity builds fast. After five years you would owe about $306,000 on the 15-year against $374,000 on the 30-year.
- It is enforced saving. The payment is mandatory, so it happens — which is not true of a plan to invest the difference.
- You own it outright fifteen years sooner, which transforms your cash flow in your fifties.
The case for 30 years
- The lower payment is a safety margin. Job loss, illness and a new baby are all easier to survive at $2,528 than at $3,349.
- You may invest the difference better. $821 a month at a 7% return for 15 years grows to about $260,000 — comparable to the interest saved, though it requires actually investing it every month.
- Retirement contributions come first. A 15-year payment that crowds out an employer 401(k) match is a bad trade, because that match is an immediate guaranteed return.
- Mortgage interest may be deductible if you itemise, though the higher standard deduction means most households no longer do.
- Inflation erodes a fixed payment. In 2041, $2,528 will feel considerably smaller than it does now.
The option most people miss
Take the 30-year loan and pay it like a 15-year one when you can. Paying $3,349 on a 30-year mortgage clears it in about seventeen years — capturing most of the interest saving while keeping the right to drop back to $2,528 in any month you need to.
You give up the 0.6-point rate advantage, which costs roughly $40,000 of the $307,000 saving on this example. What you buy with that $40,000 is the ability to stop overpaying without defaulting.
Confirm your servicer applies extra payments to principal rather than pre-paying the next instalment — some do the latter by default, which achieves almost nothing.
How to decide
| If this is true | Lean toward |
|---|---|
| The 15-year payment is under 25% of take-home pay | 15-year |
| You have 6+ months of expenses saved | 15-year |
| Employer 401(k) match already maxed | 15-year |
| Income is variable or commission-based | 30-year |
| You have high-interest debt outstanding | 30-year, clear the debt first |
| You may move within 7 years | 30-year |
| You are behind on retirement savings | 30-year, invest the difference |
Frequently asked questions
Is a 15-year mortgage worth it?
If the payment fits comfortably alongside a full emergency fund and adequate retirement contributions, yes — the interest saving is very large. If it would consume the margin that protects you against job loss, the 30-year is the better risk-adjusted choice.
Can I switch from a 30-year to a 15-year later?
Only by refinancing, which means new closing costs and whatever rate exists then. Paying extra on a 30-year achieves nearly the same result with no fee and no commitment.
Is it better to invest or pay off the mortgage early?
Mathematically, investing wins when your expected return exceeds the mortgage rate — plausible at 6.5% but not guaranteed. Paying down is a certain, tax-free return. Most people do best splitting: capture the full employer match, then overpay.
Does paying extra each month really help?
Substantially, because every extra dollar removes all future interest on that dollar. One extra payment a year typically removes four to six years from a 30-year loan.
What about a 20-year mortgage?
A reasonable middle ground that many lenders offer with a small rate discount. It saves considerably more interest than 30 years while asking for far less than the 15-year payment.
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Everything above, worked out for your own numbers in a few seconds.
Related guides
This guide is general information from ToolNest, not financial, legal or tax advice. Figures are estimates based on the assumptions stated and current at the time of writing. For decisions that matter, speak to a qualified professional in your own country.