15-year vs 30-year mortgage
By David Chen · Published September 26, 2026
Both terms buy the same house. The property does not change, the interest rate is often similar, and the lender is the same. Everything that differs comes from one thing: how long the balance is allowed to sit there. This guide puts the same $300,000 at 6.50% on both clocks and works through what each one costs — monthly, in total, and in what it lets you buy.
The same loan on two clocks
| Term | Monthly principal & interest | Total interest | Total repaid | Principal overtakes interest |
|---|---|---|---|---|
| 15 years | $2,613.32 | $170,398 | $470,398 | Month 53 |
| 30 years | $1,896.20 | $382,633 | $682,633 | Month 233 |
$300,000 at 6.50% held constant across both terms. Produced by our calculator and independently recomputed.
The 15-year payment is $717.12 a month higher. In exchange it removes $212,235 of interest. Put those two numbers next to each other and the shape of the decision becomes clear: you are buying a $212,235 discount with $717.12 of monthly cash flow, and the purchase only completes if you can make every one of the 180 payments.
Where the $212,235 comes from
The interest difference is not a penalty charged for borrowing longer. It is the mechanical result of how amortisation front-loads interest, and the last column of the table is the clearest way to see it.
On the 30-year loan at 6.50%, the first payment is $1,625.00 of interest and only $271.20 of principal. That ratio persists for nineteen years: principal does not overtake interest until month 233. By the time you are finally paying down more than you are paying for the privilege of borrowing, two-thirds of the loan term is gone.
The 15-year loan starts with the identical $1,625.00 of interest — the rate and balance are the same — but the larger payment means $988.32 goes to principal in the first month instead of $271.20. Principal overtakes interest at month 53. Compression, not thrift, is where the saving comes from.
Buying the 30-year and paying it like a 15
The 30-year contract does not oblige you to take 30 years. Extra payments go straight against principal, which shortens the term rather than reducing the payment. Here is what that looks like on the same $300,000 at 6.50%, starting from the 30-year schedule:
| Extra each month | Paid off in | Total interest | Saved against the base |
|---|---|---|---|
| $0 (as scheduled) | 360 months — 30 years | $382,633 | — |
| $250 | 262 months — 21 yr 10 mo | $262,297 | $120,337 |
| $500 | 210 months — 17 yr 6 mo | $202,874 | $179,759 |
| $700 | 183 months — 15 yr 3 mo | $172,555 | $210,078 |
Extra payments assumed to begin with the first payment. Interest saved is measured against the $382,633 of the unaccelerated 30-year loan.
An extra $500 a month retires the loan in 210 months and saves $179,759. That is most of the 15-year benefit — $212,235 — without signing a contract that requires it. An extra $700 gets closer still, clearing the balance in 183 months with $210,078 saved.
The asymmetry is the point. A 30-year loan with voluntary overpayments can be slowed to the minimum in a bad year; a 15-year loan cannot. If you lose income, the 15-year obligation is the one that defaults. The price of that flexibility is the discipline required to keep paying — and, realistically, many borrowers who intend to overpay do not.
The term changes what you can buy
This is the part that rarely makes it into the comparison, and it is frequently decisive. Lenders assess you against a payment, so a larger required payment reduces the loan you qualify for. Holding the down payment at $60,000 and the rate at 6.50%, and applying the 28/36 limits:
| Household income | Affordable at 15 years | Affordable at 30 years | Difference |
|---|---|---|---|
| $80,000 | $230,596 | $286,300 | $55,704 |
| $100,000 | $278,651 | $334,427 | $55,776 |
| $120,000 | $315,733 | $394,740 | $79,007 |
| $140,000 | $361,811 | $455,054 | $93,242 |
28% housing / 36% total debt, $500 of existing monthly debts, 1.2% property tax, $1,800 insurance a year. Computed by our affordability calculator and independently recomputed.
At $100,000 of income the difference is about $55,800 — in many markets that is the difference between a two-bedroom and a three-bedroom. Choosing the 15-year term is therefore not only a decision about how to repay a loan you have already chosen; it is a decision about which houses are available to you at all.
To see the reverse direction — what price a given income supports at each term — use the affordability calculator, which runs this arithmetic on your own numbers.
What the shorter term does not do
- It does not make you wealthier by itself. The saving is real but it arrives as the absence of a cost, spread across fifteen years. It is not a return on investment; it is a reduction in what you pay.
- It does not leave room for a bad year. The payment is fixed and the obligation is contractual. A 15-year loan taken at the limit of affordability converts a temporary income problem into a default risk.
- It ties up money that had other uses. Whether that matters depends on what else the money would have done — paying down higher-rate debt, building a reserve, or simply covering a period of reduced income.
- It does not eliminate the cost of the house. Property tax, insurance and maintenance cost the same on both terms. See the mortgage calculator for the full monthly figure.
How to decide
Work through these in order, because each one can settle the question before the next:
- Can you make the 15-year payment with the same ease as the 30-year payment, after the reserve is funded? If not, the question is answered — take the 30-year and overpay when you can.
- Is the higher payment more than about a quarter of your take-home pay? That is a warning sign regardless of what a ratio says.
- Does the 15-year term price you out of the house you need? Compare the two rows in the affordability table above with the market you are actually shopping in.
- If you take the 30-year, will the overpayment actually happen? The honest answer is found in your last twelve months of bank statements, not your intentions.
Run both scenarios through the amortization schedule before deciding, so you are looking at your own figures rather than this guide's.
The short version
On a $300,000 loan at 6.50%, the 15-year term costs $717.12 more a month and $212,235 less in interest, and clears the balance 180 months sooner. The 30-year term can reproduce most of that saving through extra payments while keeping the option to stop. The tie-breaker is rarely the mathematics — which is unambiguous — but whether your income can carry the higher fixed payment through a bad year, and whether the larger permitted loan at 30 years is what gets you the house you need.
Frequently asked questions
Is a 15-year mortgage always better than a 30-year?
It is cheaper in total interest and more expensive every month, and which of those matters more depends on your income stability rather than your discipline. The 30-year payment is $1,896.20 on the example in this guide and the 15-year is $2,613.32. If the higher payment would leave you without a reserve, the lower interest bill is not worth the risk of missing a payment — and the 30-year can always be paid down faster, while a 15-year payment cannot be reduced without refinancing.
How much interest does a 15-year mortgage save?
On a $300,000 loan at 6.50%, the 15-year term costs $170,398 of interest and the 30-year term costs $382,633. The difference is $212,235. Note that this comparison holds the rate constant; in practice a 15-year loan is often quoted at a slightly lower rate because the lender carries less risk for less time, which widens the gap further.
When does principal exceed interest on each term?
Month 53 on the 15-year loan and month 233 on the 30-year loan. That single number explains most of the interest difference: for the first four and a half years of the shorter loan, and the first nineteen years of the longer one, more than half of every payment is interest rather than principal. Shortening the term compresses that front-loaded period.
Can I get the 15-year benefit on a 30-year loan?
Largely yes, by paying extra — and you keep the option to stop. Adding $500 a month to the 30-year loan clears it in 210 months instead of 360 and saves $179,759 of interest, which is most of the way to the 15-year result. The catch is that the extra payment only happens if you actually make it every month, whereas the 15-year contract makes it for you.
Does a shorter term mean I can afford less house?
Yes, and by more than most people expect. On a $100,000 income and $60,000 down, the 30-year term supports about $334,400 of house while the 15-year term supports about $278,700 — a difference of roughly $55,800, or about one bedroom in many markets. The term is not just a repayment choice; it changes the price you can consider.
Related guides
- How much house can I afford? — Why the price a lender approves is not the price you should pay, how the debt-to-income rules work, and what the monthly figure has to cover beyond principal and interest.
- Refinance break-even point — How to work out the month a refinance pays for itself, why a shorter term can raise your payment and still save six figures, and when not to refinance.
- Biweekly payments: what they really save — How paying half your mortgage every two weeks works, the exact saving on a worked loan, and the fees and pitfalls to avoid first.
- How loan amortization works — The formula term by term, a worked month-by-month example, when principal finally overtakes interest, and why extra early payments save so much.
Run your own numbers in the loan calculator.
Calculators for this topic
- Mortgage calculator — Monthly payment with property tax, home insurance, HOA and PMI folded in — the number that actually leaves your account, not just principal and interest.
- Home affordability calculator — Works the mortgage question backwards: start from your income, debts and down payment, and find the price you can actually carry rather than the price a lender will approve.
- Amortization schedule — The full month-by-month and year-by-year breakdown of a fixed-rate loan, and how much interest an extra payment removes from the end of it.
This guide is educational and is not financial advice. Figures were produced by our calculator and independently recomputed before publication; your lender's own documents govern your loan. Spot an error? Tell us — see also our disclaimer.