ARM Calculator

Estimate how your payment could change on an adjustable-rate mortgage once the fixed period ends. Shows two honest scenarios — what happens if rates stay flat, and the worst case if they rise the maximum allowed at every adjustment — instead of pretending to predict future rates.

Want a fixed-rate comparison instead? See our Mortgage Amortization Calculator, or all our calculators.

Your Loan

Loan Amount:

Initial Fixed Rate (%):

Years Fixed (e.g. 5 for a 5/6 ARM):

Total Loan Term (years):

Adjusts Every (months, 6 for modern conforming ARMs):

Index, Margin & Caps

Current Index Value (%, e.g. 30-day Average SOFR):

Margin (%):

Initial Adjustment Cap (%):

Periodic Adjustment Cap (%):

Lifetime Cap (%):

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Worst-Case Payment (At Lifetime Cap)

at —

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Fixed-Period Payment	$0
Payment If Index Stays Flat (first adjustment)	$0

Adjustment Schedule

Year	If Index Stays Flat		Worst Case

Glossary

What Do the Cap Numbers Mean?

A “2/1/5” cap structure (common on today’s conforming SOFR ARMs) means: your rate can move at most 2% at the very first adjustment, at most 1% at each adjustment after that, and at most 5% total above your starting rate for the life of the loan — no matter how high the index goes. Your rate also can’t fall below your margin.

What’s the Difference Between 5/1 and 5/6 ARMs?

Both fix your rate for the first 5 years. A 5/1 ARM (the older convention, still used on some jumbo/portfolio loans) then adjusts annually. A 5/6 ARM (the current standard for conforming Fannie Mae/Freddie Mac loans) adjusts every 6 months instead — more frequent, smaller individual moves.

Why Two Scenarios Instead of One Prediction?

No one can predict where SOFR will be in 3 years, let alone 20. “If the index stays flat” shows a real, useful planning number using today’s rate. “Worst case” shows the maximum your payment could legally reach under your loan’s caps — the number you genuinely need to be able to afford, not just hope for.

Where Do I Find My Loan’s Actual Index, Margin, and Caps?

Your loan estimate and closing documents (specifically the ARM disclosure / Adjustable Rate Rider) state your exact index, margin, and cap structure. The defaults here are realistic examples for a typical conforming SOFR ARM, not a quote for your specific loan — always confirm with your lender.

Disclaimer: NestApple’s ARM Calculator is an estimate for reference purposes only. It models future rate scenarios based on inputs you provide and cannot predict actual future interest rates. Default values shown (index, margin, caps) are realistic examples, not a quote for any specific loan. Always confirm your loan’s actual terms with your lender. NestApple and its affiliates do not provide tax, legal, or financial advice. NestApple is a licensed real estate broker and professional service provider.