Fixed vs. ARM Payment Calculator

Compare a fixed-rate payment with an ARM using rates you enter: the payment during the initial period, after each adjustment at a rate you test, and the most the caps allow.

The loan
The rate on the fixed-rate loan you're comparing. Use your own quote.
The ARM
From your own quote.
Any rate you want to test. We don't predict rates. Caps are applied.

How the math works

  • Payments use the standard amortization formula for the rate and remaining term.
  • At each ARM adjustment, the rate moves toward the rate you entered, but no more than the first or later cap, and never past the lifetime cap from the initial rate. The payment is then recalculated over the remaining months.
  • The "highest" table applies the caps as if index + margin were always above them. That is the cap limit, not a forecast.

For definitions, read the fixed vs. ARM guide and mortgage loan types.

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Frequently asked questions

Does this calculator predict ARM rates?

No. You enter the rates. It shows the payments for the rates you type and the most the caps allow.

What payment does it show?

Principal and interest only, without taxes, insurance or mortgage insurance.

Why does the ARM payment change even if the test rate is reached right away?

Each adjustment is limited by the caps, so the rate may take more than one adjustment to reach your test rate.

Where do I get the cap numbers?

From your loan's terms. The Loan Estimate and ARM disclosure list the caps, index, margin and the most the payment can be.

Sources (Checked November 2026)

Free education only. Not tax, legal, investment or retirement-planning advice, and not a recommendation to open, fund, buy, sell or hold any account, investment or product. Enhance Finance LLC does not sell investments or financial products. Rules change, so confirm with the official source linked on this page (such as the IRS, the Social Security Administration, the CT Department of Revenue Services or the NC Department of Revenue) before you act, and ask a tax professional about your own situation.

Want your mortgage interest, points and property taxes handled correctly on your return?

Book a call with Andrew

Or call (475) 242-7941. Services are priced by quote.

Enhance Finance LLC · Andrew Nocera, Tax Preparer & Small-Business Finance Consultant. Based in Connecticut and working with North Carolina clients remotely.

Not tax, legal or investment advice. Figures are estimates for education. Checked November 2026.