15 vs 30 Year Mortgage

The 15-year mortgage is the single biggest interest saver in the entire mortgage market — but it comes at a real cost in monthly cash flow. Most of the "15 vs 30" debate reduces to one honest trade: a 15-year loan forces you to be debt-free in half the time, and charges you a lot more each month to do it. Here is the full comparison on real numbers.

Switch the term on the HomeMath mortgage calculator to see both scenarios on your own loan.

The 15-year advantage: interest savings

A shorter term attacks the balance twice as fast, so interest — which is charged on the remaining balance — has half as long to accumulate. On a $400,000 loan at 6.5%, here is the head-to-head:

	30-year	15-year
Monthly P&I	$2,528	$3,485
Total interest	$510,000	$227,000
Total paid	$910,000	$627,000

The 15-year saves roughly $283,000 in interest — more than two-thirds of the 30-year's interest bill. And this understates the real advantage, because 15-year loans usually carry a lower rate than 30-year loans (often about half a point), which widens the gap further.

The 15-year cost: cash flow

The flip side is the payment itself. On that same $400,000 loan, the 15-year costs about $957 more every month — roughly 38% higher. You are repaying the same principal in half the time, so each payment is much larger.

That higher payment is locked in. A 30-year borrower who loses a job can tighten elsewhere and still make the smaller payment; a 15-year borrower has far less room to maneuver. The 15-year's savings only materialize if you actually make all 180 payments — the plan fails the moment you cannot.

Why the 15-year also builds equity faster

Beyond interest, the 15-year turns you into a homeowner faster in the equity sense. Because more of each early payment goes to principal (the balance is falling twice as fast), you cross the 20% equity mark in about a third of the time. That matters if you might want a home equity line, or if you might sell in a decade — you walk away with far more cash.

With a 30-year loan in its first years, you are mostly renting the money: after five years you have paid off only about 6% of the balance. With a 15-year, after five years you have paid off over 25% of it. That is the difference between owning a home and owning a loan.

The middle path most people ignore

You do not have to choose between the two extremes. Take the 30-year loan for flexibility, then pay extra as if it were a 15-year. Add the difference — about $957 a month in this example — as an extra principal payment, and you approximate the 15-year's payoff date and most of its interest savings.

The benefit is optionality. If money gets tight, you simply stop the extra payments and fall back to the lower 30-year minimum. The 15-year offers no such escape hatch. The cost is a slightly higher 30-year rate and the discipline to actually make the extra payments — which, honestly, most people do not keep up without automation.

How to decide

The 15-year is right when all of these are true:

• The higher payment fits comfortably under 28% of your gross income.
• You have a full emergency fund — six months of expenses — separate from the down payment.
• You are already maxing out retirement savings, so the extra payment is not crowding out better uses of the money.
• You want to be debt-free by a specific date, like retirement.

The 30-year — or the 30-year-plus-extra-payments hybrid — is right when your budget is tighter, your income is variable, or you would rather keep the extra cash invested. A 6.5% mortgage is cheap debt; paying it off early competes with investing that money at a potentially higher return. That is a personal call, not a one-size answer.

Frequently asked questions

How much more is a 15-year payment?

Roughly 35% to 40% more than a 30-year payment for the same loan amount, because you repay the same principal in half the time. Use the term dropdown on the calculator for your exact numbers.

Is a 15-year rate lower than a 30-year?

Usually yes, by about 0.25% to 0.75%. The shorter term is less risk for the lender, and the market prices that in.

Can I pay my 30-year like a 15-year?

Yes. Make extra principal payments equal to the difference between the two payments, and you capture most of the 15-year's interest savings while keeping the lower required payment.

Should I refinance from a 30-year to a 15-year?

Only if the higher payment is comfortable and you plan to stay long enough to recoup the refinance closing costs. Otherwise, adding extra principal to your existing 30-year achieves most of the same result for free.

Compare 15-year and 30-year payments on your own numbers with the HomeMath mortgage calculator.