Adjustable-Rate Mortgage Calculator

Type a rate you want to worry about. The page applies your caps and prices the remaining balance. It does not forecast the index.

Written for Equidwell and last checked in October 2026. We build the calculators on this site. We are not a lender, and this page is not advice for your loan.

The scenario rate is a rate you want to test. It is not a forecast. Caps limit how high this model lets that test go.

Loan amount

Full term in years

Initial rate

Example rate, not a live quote.

Years before the first adjustment

Rate to test after the first adjustment

Periodic cap

Lifetime cap above the initial rate

First payment month

Initial payment $1,918.56

Balance after the initial period $297,774.07

First adjustment cannot exceed 8.000% in this model.

Lifetime maximum rate 11.000%

Tested rate actually used 8.000%

Payment at the tested rate $2,298.27

Payment at the lifetime cap $2,918.52

Neither future payment is guaranteed. The index and margin on a real ARM note control the adjustment, subject to the caps in that note.

How this calculator works

The initial payment amortizes the full term at the initial rate.
After the initial period, the model takes the remaining balance.
The tested rate cannot rise above the periodic cap or the lifetime cap.
A new payment is calculated on the remaining balance and remaining years.

Caps limit the test, they do not predict the index

A real ARM note names an index and a margin. After the fixed period, the rate is that sum, held in by the caps. This page does not look up an index.

The scenario box is a what-if. If you type a rate above the cap, the result shows the capped rate it actually used. It will not quietly price the impossible number.

Sources

CFPB: Owning a home

Common questions

Will my payment become the lifetime-cap payment?

Not necessarily. That line is the high end of this model if the rate reaches the lifetime cap and the loan is recast on the remaining balance. Your note controls the real adjustment.

Does the initial payment include taxes and insurance?

No. This calculator is principal and interest only.

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Longer guides on these topics are linked from the guides library.