15 vs 30 Year Mortgage Calculator
The house, the two terms, and what the difference earns
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General model; U.S.-specific rules are identified on the relevant tool
- Scope and limitations
- Educational estimate only. A lender may use different compounding, day-count, eligibility, tax, insurance, escrow, fee, or rounding rules.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter the home price and your down payment.
- 02
Enter each term with its own rate. A 15-year loan genuinely prices below a 30-year one, and that spread is half the argument — use the two quotes you were actually given.
- 03
Add annual property tax, insurance and the PMI rate, so both payments are the real ones.
- 04
Enter the return you would earn investing the payment difference.
- 05
Read the two payments and the lifetime interest gap, then the net worth each path leaves at the longer term's end.
Formula
Each payment is the level amount that amortizes the loan over its term, plus escrow and PMI until the balance reaches the cancellation LTV. Both households then spend the shorter term's monthly outlay for the whole horizon and invest whatever housing does not take, and the comparison is portfolio plus home equity at the end.
Example
A $420,000 home with $63,000 down, 15 years at 5.75% against 30 at 6.5%: $3,678 a month versus $2,970, a $708 gap. The 15-year avoids $278,712 of interest, sheds PMI at 1 year 10 months rather than 6 years 2 months, and owns the house outright at year 15 when the 30-year borrower still owes about $259,000. Investing the difference at 7% throughout, the 15-year path ends about $404,398 ahead at year 30.
Definitions
- PMI
- Private mortgage insurance, charged while the loan-to-value is above the cancellation threshold — 78% by default here.
- Escrow
- Property tax and homeowners insurance collected with the payment. It is the same under either term.
- Invest-the-difference
- The assumption that the money a longer term frees up each month is actually invested rather than spent.
Good to know
The same house, two different loans
The choice between a 15-year and a 30-year mortgage is usually presented as a trade between a payment you can afford and interest you would rather not pay, and on the defaults here that trade is stark: $3,678 a month against $2,970, and $278,712 of interest avoided over the life of the loan. But the interest figure alone is a poor way to decide, because it ignores what happens to the $708 a month the longer loan frees up. If that money is invested, the 30-year borrower is running a leveraged position — borrowing at the mortgage rate to invest at a market rate — and the comparison becomes a question about returns rather than about interest.
Both households, to the same date
The commonest error in this comparison is to stop the model at the shorter term's payoff. Do that, and the 30-year borrower is credited with fifteen years of investing the difference while the 15-year borrower's advantage — a paid-off house and no mortgage payment at all — is simply cut off before it counts. This page holds both households to the same monthly outlay for the full thirty years. While both loans run, the longer term invests the difference; once the shorter loan is gone, that household invests its entire former payment. The headline model then assumes the longer-term household spends the difference after year 15, which is what most people actually do, and reports the disciplined alternative separately so the assumption is visible rather than buried.
The two costs a payment comparison misses
Two real differences never show up in the monthly figure. The first is the rate itself: 15-year money genuinely prices below 30-year money, often by half a point or more, because the lender's risk is shorter — which is why this page insists on a rate per term rather than one rate for both. The second is mortgage insurance. PMI comes off when the balance reaches the cancellation loan-to-value, and a 15-year loan amortizes there far faster: under two years on the defaults against more than six. That is several thousand dollars the payment comparison never sees, and it is one of the reasons a shorter term is cheaper than it first appears.
The deduction most borrowers no longer get
Older comparisons lean on the mortgage interest deduction to argue for the longer term — more interest, more deduction. That argument mostly stopped working in 2018. With a standard deduction of $16,100 single and $32,200 married filing jointly for 2026, a household needs a large amount of interest, state and local tax and charitable giving before itemizing beats simply taking the standard amount, and most no longer clear it. Only interest above that threshold is worth anything at all, and only at your marginal rate. That is why the deduction field on this page opens at zero: a friendlier default would hand every visitor a benefit most of them do not receive, and would do it in the direction that flatters the 30-year loan.
Frequently asked questions
Why does the comparison run to 30 years rather than 15?
Because stopping at year 15 hands the answer to the 30-year loan by construction. Years 16 to 30 are exactly when the 15-year borrower's mortgage is gone and their whole former payment goes into the market. Both households are held to the same monthly outlay for the full horizon so neither is quietly given a spending advantage.
Is the 15-year always better?
On these defaults yes, but the invest-the-difference return is what decides it, and the page reports the return the 30-year would need to break even. Above that rate the longer term wins — if the difference is genuinely invested every month, which is the assumption that most often fails in real life.
Why does the mortgage interest deduction default to zero?
Because most borrowers no longer itemize. With a standard deduction of $16,100 single and $32,200 joint in 2026, mortgage interest is worth nothing to a household that does not clear it. A default that hands everyone a deduction would quietly overstate the 30-year loan's case, so the field asks what share you actually deduct.
Why does PMI drop at different times?
Mortgage insurance comes off when the balance reaches the cancellation loan-to-value, and a 15-year loan gets there years sooner because it amortizes faster. On the defaults it is under two years against more than six — a real cost difference that a payment-only comparison misses.
Why is there no house appreciation?
The same house appreciates identically under either loan, so a growth rate would move both net worths by the same amount and never change the verdict — while making a calculation look like a forecast.
I want to compare 10 against 20 years.
Type them in. The two term fields take any pair; the page is named for the comparison people search for, not limited to it.