Penny Runs the NumbersOn the median US home ($417,500, 20% down), a 50-year mortgage at an assumed 7.68% lowers the payment by about $77 a month versus a 30-year loan at 7.18%, but costs $496,539 more in interest. After 10 years you have repaid only $8,545 of the 50-year loan.
What the calculator shows
Set the home price, the down payment and both interest rates. The cards show the monthly payment, the total interest over the life of each loan and how much is still owed in any year you pick on the chart.
The default numbers are the median existing-home price from the National Association of Realtors and the latest 30-year average from Freddie Mac's weekly survey. The 50-year rate is an assumption, because no mainstream 50-year mortgage is sold yet.
Why the 50-year loan saves so little per month
Stretching a loan from 30 to 50 years mostly stretches the interest, not the principal. With the same 7.18% rate the payment drops by about $207 a month. Lenders charge more for longer loans, though. At a half-point higher rate the saving shrinks to about $77, and at about 0.8 points higher (7.98%) it disappears completely.
Meanwhile the balance barely moves. After 10 years of payments on the 50-year loan you have repaid just $8,545. When the 30-year loan is paid off, the 50-year loan still has $267,579 left.
Could you invest the difference instead?
To come out even, the $77 a month you save would have to grow fast enough to cover what you still owe on the 50-year loan when the 30-year loan ends. That takes about 11.9% a year, every year, for 30 years, before tax.
Questions
Is a 50-year mortgage cheaper per month?
Only slightly. On a $334,000 loan the payment is $2,263 at 7.18% over 30 years and $2,185 at 7.68% over 50 years, a difference of about $77 a month. If the 50-year rate is 0.8 points or more above the 30-year rate, the 50-year payment is higher.
How much more interest does a 50-year mortgage cost?
With the default inputs, total interest is $480,548 on the 30-year loan and $977,087 on the 50-year loan: $496,539 more.
What interest rate do 50-year mortgages have?
There is no broadly available 50-year product yet, so there is no market rate. We assume the 30-year rate plus 0.50 points, the middle of published estimates (0.4 to 1.5 points). Use the 50-year rate slider to test other spreads.
What does this calculator leave out?
It counts principal and interest only: no property tax, insurance, PMI or HOA, no home price growth, no extra payments or refinancing.
Sources and assumptions
- 30-year fixed-rate mortgage average, week of 2026-11-05: Freddie Mac Primary Mortgage Market Survey (PMMS) (checked 2026-11-11)
- Median existing-home price, all housing types, September 2026: National Association of Realtors, Existing-Home Sales (released 2026-10-13) (checked 2026-11-11)
- Reference: www.housingwire.com
- Reference: www.thetruthaboutmortgage.com
- Reference: wolfstreet.com
- Reference: www.ubs.com
- Principal and interest only: no property tax, insurance, PMI or HOA.
- No home price appreciation in equity figures (equity = price - remaining balance).
- Monthly compounding, payments at month end, no extra payments, no refinancing.
- Break-even return: monthly payment difference invested every month for 30 years must grow to the 50-year loan's balance at year 30 (when the 30-year loan is paid off). Pre-tax.
Last updated 2026-11-11.