Does the 15-year rate always beat the 30-year rate?

Usually, but the gap moves with market conditions. Lenders generally offer a lower rate on 15-year loans because the shorter repayment window reduces their risk. In these examples a 0.75-point gap is used, but the real spread on any given day could be smaller or larger. Enter the exact rates you are quoted for the most accurate comparison.

Is the 30-year really twice as expensive as the 15-year?

No — it is typically more expensive than twice the interest in dollar terms when the 30-year carries a higher rate. In the $280,000 example, the 30-year interest is $373,787 versus $145,304 for the 15-year, a ratio of about 2.6 to 1. The extra cost comes from both the longer period and the higher rate.

What if I make extra payments on my 30-year?

Extra principal payments shorten the effective term and reduce total interest. If you consistently pay even $200 more per month on a 30-year, you will retire the loan years early and reclaim a meaningful slice of the interest savings. The MortgageLab calculator shows the total interest for a clean fixed term; for extra-payment scenarios, compare the two clean terms first to understand the baseline.

Do these numbers include taxes, insurance, or PMI?

No. The figures above are pure principal-and-interest amortization on a 20%-down loan (no PMI applies). Property tax, homeowners insurance, PMI, and HOA dues add to the monthly payment but do not change the principal-and-interest comparison between the two terms.

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How much more interest does a 30-year mortgage cost than a 15-year?

By MortgageLab · Published June 10, 2026 · Updated June 10, 2026

On a $280,000 loan at example rates of 6.75% (30-year) and 6.00% (15-year), the 30-year term costs $228,483 more in total interest — $373,787 versus $145,304 — even though its monthly payment is $547 lower.

The core trade-off in numbers

A 30-year mortgage keeps the monthly payment manageable by spreading repayment across 360 months, but interest accumulates slowly on a balance that falls slowly. A 15-year loan compresses the same principal into 180 months, which forces more principal off the balance each month and leaves far less balance to charge interest against.

These are estimates computed with the MortgageLab amortization engine using example rates — they are not a rate lock or financial advice. Real quoted rates vary by lender, credit profile, and market conditions; lenders typically offer a lower rate on 15-year loans because the shorter term reduces their exposure, which is why the two examples use distinct rates.

Worked example — $350,000 home, 20% down

Assumptions: $350,000 purchase price, $70,000 down payment (20%), $280,000 loan. Example rate of 6.75% for the 30-year loan and 6.00% for the 15-year loan (rates are clearly labeled examples, not current market averages). The 30-year monthly principal-and-interest payment is $1,816.07; total repaid over 360 months is $653,787; total interest is $373,787. The 15-year monthly payment is $2,362.80; total repaid over 180 months is $425,304; total interest is $145,304.

Choosing the 15-year term in this scenario saves $228,483 in interest over the life of the loan. The cost is a higher required payment of $546.73 more per month. That extra $547 is the price of paying the loan off 15 years earlier and keeping $228,483 from going to the lender as interest.

Smaller loan — $200,000 home, 20% down

On a smaller purchase — $200,000 home, $40,000 down, $160,000 loan — the gap is proportionally similar. At the same example rates (6.75% 30-year, 6.00% 15-year), the 30-year payment is $1,037.76 per month with $213,593 in total interest. The 15-year payment is $1,350.17 with $83,031 in total interest.

That is $130,562 in interest savings for a higher monthly commitment of $312.41. Both examples show the same pattern: a longer term roughly multiplies interest by 2.5 to 2.6 relative to a 15-year at a slightly lower rate, not just by 2, because the interest rate on the 30-year loan is higher and the balance stays elevated for longer.

Why the savings exceed what you might expect

Many people expect the 30-year to cost roughly twice the interest of a 15-year, since the term is twice as long. The actual ratio is higher for two reasons. First, lenders usually price 15-year loans at a lower rate, because a shorter loan carries less risk — in these examples the gap is 0.75 percentage points. Second, amortization front-loads interest payments: early in a 30-year loan most of each payment is interest, so the principal falls slowly and the interest meter runs for a long time.

In the $280,000 example, the 30-year borrower pays more in total than they borrowed ($653,787 repaid on a $280,000 loan) — the interest cost alone is larger than the original loan. The 15-year borrower pays back $425,304, of which only $145,304 is interest, and is done in half the time. The ratio of 30-year to 15-year interest in this example is approximately 2.57 to 1, not 2 to 1, because the rate difference and front-loading compound together.

Reading the total-repaid figure

Beyond the interest comparison, the total-repaid figure puts the cost of each term in plain terms. On the $280,000 loan at the example rates, the 30-year borrower sends $653,787 to the lender over 360 months. The 15-year borrower sends $425,304 over 180 months. The difference — $228,483 — is entirely interest, money that goes to the lender rather than building equity or staying in your account. Seeing the total-repaid figure next to the monthly payment is often the clearest way to grasp the trade-off.

On the smaller $160,000 loan, the gap is $130,562 ($373,593 total repaid for the 30-year versus $243,031 for the 15-year). In both cases the 15-year borrower repays far less in total, even after paying a higher monthly amount every month for 15 years. The monthly payments are bigger, but the overall financial outcome is dramatically different.

How to use this information

The monthly payment difference is what most budgets feel. Use the MortgageLab calculator to enter your own numbers and compare the total interest line for each term. If the higher 15-year payment fits comfortably in your budget, the interest saving is substantial. If it would strain cash flow, a 30-year loan with occasional extra principal payments can reclaim part of the saving without locking you into the higher required payment.

These are estimates only. The figures above use example fixed rates for illustration; your actual savings depend on the exact rates you are quoted, whether you keep the loan for the full term, and any extra payments you make. Always run the comparison with the rates a lender quotes you before making a borrowing decision.

Questions

Does the 15-year rate always beat the 30-year rate?: Usually, but the gap moves with market conditions. Lenders generally offer a lower rate on 15-year loans because the shorter repayment window reduces their risk. In these examples a 0.75-point gap is used, but the real spread on any given day could be smaller or larger. Enter the exact rates you are quoted for the most accurate comparison.
Is the 30-year really twice as expensive as the 15-year?: No — it is typically more expensive than twice the interest in dollar terms when the 30-year carries a higher rate. In the $280,000 example, the 30-year interest is $373,787 versus $145,304 for the 15-year, a ratio of about 2.6 to 1. The extra cost comes from both the longer period and the higher rate.
What if I make extra payments on my 30-year?: Extra principal payments shorten the effective term and reduce total interest. If you consistently pay even $200 more per month on a 30-year, you will retire the loan years early and reclaim a meaningful slice of the interest savings. The MortgageLab calculator shows the total interest for a clean fixed term; for extra-payment scenarios, compare the two clean terms first to understand the baseline.
Do these numbers include taxes, insurance, or PMI?: No. The figures above are pure principal-and-interest amortization on a 20%-down loan (no PMI applies). Property tax, homeowners insurance, PMI, and HOA dues add to the monthly payment but do not change the principal-and-interest comparison between the two terms.