ARM Mortgage Calculator

An adjustable-rate mortgage is fixed for a few years and then resets against an index, so the useful question is how high the payment can go. Enter the loan, the starting rate and fixed period, the initial, periodic and lifetime caps from the note, and optionally the index and margin, and this returns the starting payment, the balance at the first reset, the capped rate and payment at each reset, the ceiling rate and the highest payment the caps permit. It also runs the fully indexed scenario and can set the whole thing against a fixed-rate loan. Every reset re-amortizes the remaining balance over the remaining term, which is why a payment jumps by more than the extra interest. Principal and interest only, and only as accurate as the caps you type in.

Enter the loan, the starting rate and fixed period, and the three caps from the note. The caps are usually printed as a set like 2/2/5.

Loan Amount ($) *

Initial Fixed Rate (%) *

Initial Fixed Period (years) *

The first number in a name like 5/1 or 7/6: how long the starting rate is locked.

Full Loan Term (years) *

Adjusts Every

Initial Adjustment Cap (%) *

The most the rate may move at the first adjustment. The first number of a 2/2/5 cap set.

Periodic Cap (%) *

The most it may move at every adjustment after the first.

Lifetime Cap (%) *

The most the rate may ever sit above the starting rate.

Current Index Rate (%)

The published index the note is tied to, such as SOFR. Optional, but with the margin it gives the fully indexed scenario.

Margin (%)

Fixed for the life of the loan and added to the index at every reset.

Fixed Rate To Compare Against (%)

Optional. The rate on a fixed-rate loan you are weighing this against.

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