ARM Calculator with Extra Payments
Calculate the full life of an adjustable-rate mortgage. Type your expected adjustment per period and the rate at every reset is filled in for you — then edit any row to model what you actually expect. Layer extra principal payments on top to see how fast you can pay it off, even if rates rise.
ARM Structure
5/1 ARM = 5, 7/1 ARM = 7, 10/1 ARM = 10
5/5 ARM = 5, most ARMs = 1
Standard ARMs limit each adjustment. Off by default — turn on to model a real ARM disclosure.
| Year | Adjustment | Adjusted rate | Effective |
|---|---|---|---|
| Year 5 | #1 | 5.500% | |
| Year 6 | #2 | 5.500% | |
| Year 7 | #3 | 5.500% | |
| Year 8 | #4 | 5.500% | |
| Year 9 | #5 | 5.500% | |
| Year 10 | #6 | 5.500% |
Every row is taken at face value. Edit individual rows to override the expected adjustment.
Model the effect of paying extra toward principal.
About This ARM Calculator with Extra Payments
This calculator models an adjustable-rate mortgage (ARM) the way you actually think about one: a fixed-rate period at the start, then a series of resets where the rate can change. Set the initial fixed period and adjustment frequency, type the rate you expect at each reset to move by, and the table fills in. Want to model a different scenario at year seven? Edit that row directly. Every change re-amortizes the remaining balance over the remaining term at the new rate, which is what real ARMs do at every reset.
Where this tool earns its keep is the extra-payments layer. Add a recurring monthly extra, a yearly lump sum, or any number of one-time payments and watch the schedule recompute live. Extra principal shortens the term — if the loan pays off before later adjustments hit, those rate increases never actually cost you anything. That's the most common reason savvy borrowers take an ARM: lock in the lower fixed-period rate, attack the principal aggressively, and exit before the resets matter.
If you're modeling a real lender's ARM with a 2/2/5 or 5/2/5 cap structure, flip on the advanced caps option to add per-adjustment and lifetime limits. For most users — comparing scenarios, modeling an existing ARM, or stress-testing what happens if rates rise — the default rate path is faster and clearer. For wrap mortgages, balloon exits, tax-benefit modeling, and full deal-structuring against a fixed loan, check out the Flexi calculator.