The trade-off, in one sentence
A 15-year mortgage costs meaningfully more each month and dramatically less over the life of the loan. Those two figures — the monthly difference and the total interest saved — are the whole decision, and the comparison above computes both from your own price, deposit and quoted rates rather than from an example that may look nothing like your loan.
The size of the gap surprises people, because it comes from two effects at once. You pay interest for half as long, and you pay it at a lower rate, since shorter terms are normally quoted below longer ones. The interest saving is therefore far larger in proportion than the payment increase — which is the entire case for the shorter term, and it is a strong one.
Why 15-year rates are lower
Fifteen-year loans consistently price below 30-year loans, typically by something in the range of half a point to three quarters of a point, though the spread widens and narrows with market conditions. Lenders charge less because a shorter loan carries less exposure to inflation and rate movement, and because borrowers who qualify for the higher payment tend to be stronger credits.
That rate discount compounds the effect of the shorter schedule. You are not only paying interest for half as long, you are paying a lower rate while you do it, which is why the interest saving is so disproportionate to the payment increase.
How amortization drives the difference
A mortgage payment is fixed, but its composition shifts. Early payments are overwhelmingly interest because interest accrues on a large balance; late payments are almost entirely principal.
On a 30-year loan at typical rates, it takes roughly 18 to 20 years before the principal portion of a payment exceeds the interest portion. A 15-year loan crosses that point within the first few years. This is also why equity accumulates so much faster on the shorter term, and the year-by-year table above shows the gap opening on your own loan amount: the shorter term carries a smaller balance from the first payment, so its equity line pulls away immediately rather than at the end.
The case for the 30-year loan
The 30-year loan's advantage is optionality, and it is genuinely valuable. The lower required payment is a floor, not a ceiling: nothing stops you from paying extra. A borrower who takes a 30-year loan and voluntarily pays the 15-year amount each month reaches a nearly identical payoff date, while retaining the right to drop back to the smaller required payment during a job loss, a medical event or a business downturn. The borrower locked into the 15-year payment has no such fallback, and missing it has consequences a missed savings deposit does not.
The cost of that insurance is the rate spread, which is real but modest. There is also an opportunity-cost argument: if you would genuinely invest the payment difference rather than spend it, directing it to a retirement account with an employer match or a tax advantage can outperform prepaying the mortgage. That argument has a break-even rather than an opinion attached to it, and the comparison above solves for it — the return those contributions must earn, after tax, for the two choices to finish level. Judge it against what you actually expect to earn. The qualifier still matters, because the discipline is rare.
Which term suits which borrower
- Choose 15 years when: your income is stable and comfortably absorbs the higher payment, you have a funded emergency reserve, you are already contributing enough to capture any employer retirement match, and retiring the debt before a known milestone such as retirement or college tuition matters to you.
- Choose 30 years when: the higher payment would crowd out emergency savings or retirement contributions, your income is variable or commission-based, you expect to move within several years, or you want a lower committed payment while voluntarily overpaying.
The middle options people overlook
Terms are not limited to 15 and 30. Many lenders write 20-year and 25-year mortgages, which capture part of the rate discount and much of the interest saving at a payment between the two extremes. A 20-year loan is often the sensible compromise for a borrower who finds the 15-year payment slightly out of reach.
Note also that qualifying for a 15-year loan is harder: the higher payment raises your debt-to-income ratio, so the same income supports a smaller 15-year loan than a 30-year one. If you are buying at the top of your budget, the shorter term may simply not be available for the house you want.
Frequently asked questions
Is a 15-year mortgage always better than a 30-year?
It is cheaper, not always better. It costs far less in total interest, but it commits you to a payment you cannot reduce. If that payment would prevent you from building an emergency fund or capturing an employer retirement match, the 30-year loan is the sounder choice.
How much interest does a 15-year mortgage actually save?
Usually well over half of it, driven both by the halved term and by the lower rate shorter loans command — but the exact figure depends on your loan size and on the two rates you are quoted, which is what the comparison at the top of this page works out. On a mid-sized loan the saving typically runs into the hundreds of thousands.
Can I get a 30-year loan and just pay it off in 15 years?
Yes, and it is a common strategy. Paying the 15-year amount on a 30-year loan produces a nearly identical payoff date while preserving the option to fall back to the lower required payment. You pay slightly more interest because the 30-year rate is higher, which is the price of the flexibility.
Is it better to take a 30-year mortgage and invest the difference?
It depends on a rate you can calculate rather than guess. The comparison on this page works out the annual return, after tax, that the invested monthly difference would need to earn to match simply taking the shorter loan. If you expect to beat that reliably — and will actually invest the money every month rather than spend it — investing wins. If not, the shorter term is the surer outcome, because its return is contractual.
Why is the 15-year interest rate lower?
Lenders face less inflation and interest rate risk over a shorter horizon, and shorter-term borrowers are typically stronger credits. The discount usually falls somewhere between half and three quarters of a percentage point.
Is it harder to qualify for a 15-year mortgage?
Generally yes. The larger required payment increases your debt-to-income ratio, so a given income qualifies you for a smaller loan on a 15-year term than on a 30-year term.
Related calculators
How this estimate is built
Principal and interest come from the standard amortization formula, worked through in full on the formula reference page. Property tax, insurance, PMI and loan-program figures layer on top from published assumptions — each one sourced, dated and listed on the methodology page. Every result here is an estimate built from public data, not a quote: confirm the specifics with a lender before relying on it.
For developers
This calculation is also available as a REST API and through an MCP server, both running the same engine as this page — so the figures match by construction rather than by convention. No key required.