15-year vs 30-year mortgage: interest cost table
At 6.5%, a $300,000 15-year mortgage costs $2,613.32 a month and $170,398 in interest; the 30-year costs $1,896.20 a month and $382,633. The shorter term saves $212,235 in interest for $717.12 more each month. The table compares both terms at every rate from 4% to 8%.
| Rate | 15-year: monthly payment | 15-year: total interest | 30-year: monthly payment | 30-year: total interest | Interest saved by 15 years |
|---|---|---|---|---|---|
| 4.0% | $2,219.06 | $99,431 | $1,432.25 | $215,609 | $116,177 |
| 4.5% | $2,294.98 | $113,096 | $1,520.06 | $247,220 | $134,124 |
| 5.0% | $2,372.38 | $127,029 | $1,610.46 | $279,767 | $152,739 |
| 5.5% | $2,451.25 | $141,225 | $1,703.37 | $313,212 | $171,987 |
| 6.0% | $2,531.57 | $155,683 | $1,798.65 | $347,515 | $191,832 |
| 6.5% | $2,613.32 | $170,398 | $1,896.20 | $382,633 | $212,235 |
| 7.0% | $2,696.48 | $185,367 | $1,995.91 | $418,527 | $233,159 |
| 7.5% | $2,781.04 | $200,587 | $2,097.64 | $455,152 | $254,565 |
| 8.0% | $2,866.96 | $216,052 | $2,201.29 | $492,466 | $276,414 |
Both columns use the same rate so the term alone is compared. In practice lenders usually price a 15-year loan a little below the 30-year, which widens the gap: read the 15-year columns one row up for a half-point cheaper rate. To try your own figures, use the mortgage calculator.
How the table is worked out
The monthly principal and interest payment is the standard formula: loan × r × (1 + r)n / ((1 + r)n − 1), where r is the annual rate divided by 12 and n is 180 or 360 months. Total interest is the payment times n, less the loan. It is the same calculation the mortgage calculator runs, checked against it in three cells when the table was built. Taxes, insurance, PMI and fees are not included.
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