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ARM vs Fixed Mortgage Calculator

Compare an adjustable-rate mortgage against a fixed-rate loan side by side, including what happens to your payment after the ARM adjusts.

Part of a topic cluster
This page is part of our Complete Mortgage Guide 2026.
Fixed-rate payment
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ARM initial payment
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ARM payment after adjustment
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Savings during ARM fixed period
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Extra cost per month after adjustment
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Break-even assessment
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How ARMs work

An adjustable-rate mortgage (ARM) offers a lower fixed rate for an initial period (commonly 5, 7, or 10 years), then adjusts periodically based on a market index plus a margin, subject to rate caps.

Total savings during fixed period = (Fixed payment − ARM payment) × months in ARM fixed period
Compare this against the potential extra cost if rates rise after adjustment, weighted by how long you expect to hold the loan.

When an ARM makes sense

ARMs are most attractive when you plan to sell or refinance before the fixed period ends, when the initial rate discount is substantial (0.75%+ below fixed), or when you expect rates to fall by the adjustment date. They carry real risk if your plans change and you hold through the adjustment during a high-rate environment.

Rate caps protect against worst-case scenarios

Modern ARMs include caps limiting how much the rate can rise at first adjustment, at each subsequent adjustment, and over the life of the loan (commonly a 2/2/5 or 5/2/5 structure). Always confirm the specific caps on any ARM offer — they materially change the worst-case payment.

Related tools

See the full new-rate payment breakdown in the Mortgage Calculator, or read the full comparison in ARM vs Fixed Rate Mortgage 2026.

Frequently asked questions

Is an ARM riskier than a fixed-rate mortgage?
Yes, in the sense that your payment can increase after the initial fixed period. The tradeoff is a lower rate during that fixed period. Rate caps limit how much it can rise, but the payment is not guaranteed to stay level like a fixed-rate loan.
What does 5/1 ARM mean?
The rate is fixed for the first 5 years, then adjusts annually (the "1") thereafter based on a market index plus a margin, subject to rate caps.
When does an ARM make sense over a fixed-rate mortgage?
When you plan to sell or refinance before the fixed period ends, when the ARM offers a meaningfully lower initial rate, or when you have strong reason to expect rates will be lower at the adjustment date.
What are ARM rate caps?
Limits on how much your rate can increase at the first adjustment, at each subsequent adjustment, and over the life of the loan. A common structure is 2/2/5 — max 2% at first adjustment, 2% at each following adjustment, 5% total over the loan life.
Can I refinance out of an ARM before it adjusts?
Yes, and many ARM borrowers plan to do exactly this — refinance into a fixed-rate loan or sell before the initial period ends, capturing the lower ARM rate without ever facing the adjustment risk.
Related tools
→ Mortgage Calculator→ Refinance Calculator→ ARM vs Fixed: Full Guide→ Amortization Calculator