15- vs 30-year mortgage calculator
Which term saves you more? Compare a 15-year and a 30-year loan side by side — the payment difference and the total interest a 15-year saves. No email, no lender attached.
Both rates prefilled from our live board (30-yr 7.424%, 15-yr 6.735%) — edit either.
15- vs 30-year mortgage: the trade-off
A 30-year loan spreads repayment over twice as long, so the monthly payment is lower and more affordable — but you borrow for longer and typically at a higher rate, so total interest is much larger. A 15-year loan costs more each month but usually carries a lower rate and pays principal down far faster, cutting total interest dramatically — often to less than half. This tool computes both payments from your loan amount and each rate, then shows the interest the 15-year saves against the extra you pay monthly to get it.
A middle path
Prefer the 30-year’s lower required payment but want the 15-year’s payoff? Take the 30-year and add extra principal — our payoff calculator shows how close that gets you, while keeping the lower payment as a safety valve.
A worked example
On a $300,000 loan, a 30-year at 6.5% runs about $1,896/month and roughly $382,000 in total interest. A 15-year at a lower 5.75% runs about $2,491/month — about $595 more each month — but only around $148,000 in total interest. That is roughly $234,000 less interest, for a payment about a third higher. The 15-year’s edge comes from two things working together: a rate that’s typically lower, and principal that’s retired in half the time.
What trips people up
- Buying more house because the 30-year “fits.” The lower 30-year payment can tempt a bigger purchase, which erases the savings. Compare both terms on the same loan amount.
- Treating the 15-year payment as flexible. It is contractual — you must make it every month. If your income varies, the 30-year-plus-extra path keeps the high payment optional.
- Ignoring the opportunity cost. The extra ~$595/month on a 15-year is money not invested elsewhere. If your rate is low and expected returns are high, the math can favor the 30-year.
Common questions
Is a 15-year mortgage worth it?
A 15-year loan carries a higher monthly payment but a lower rate and far less total interest — often less than half — because you borrow for half as long and pay principal faster. It is worth it if you can comfortably afford the higher payment; the trade-off is less monthly flexibility.
Why is the 15-year rate lower?
Lenders take on less risk over a shorter term, so 15-year fixed rates typically run a bit below 30-year fixed rates. The combination of a lower rate and a shorter term is what drives the large interest savings.
Can I just pay extra on a 30-year instead?
Yes — a 30-year loan with extra principal each month can mimic a 15-year payoff while keeping the lower required payment as a safety valve. You give up the slightly lower 15-year rate. Our payoff calculator shows the extra-payment version.
By L.W. Martin, Founder — 20 years in the mortgage business, including 15 running his own brokerage. About → · Updated September 2026.