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ARM vs Fixed-Rate Mortgage Calculator

Compare an adjustable-rate mortgage to a fixed-rate mortgage over your planned hold period. See intro and post-adjustment payments and which option costs less in total.

Loan basics

Loan amount

Term (years)

Years you'll hold

Fixed-rate option

Fixed rate

ARM option

Intro rate

Intro years

Post-intro expected rate

Fixed

$2,661/mo

consistent payment for 30 years

Total over hold: $287,411

ARM intro

$2,463/mo

first 7 years

Then $2,857/mo at expected rate

ARM total over hold

$275,461

$11,950 less than fixed

Decision framework

You'll hold past the intro period, so you're exposed to 2 years at the post-intro rate. The ARM still wins here in this scenario, but rate movement could flip the answer.

ARMs typically price 0.25–0.75% below 30-year fixed. Use them when (a) your hold is short, (b) you can absorb the worst-case payment if rates rise, or (c) you have a clear refinance plan ahead of the adjustment.

Editorial noteMaintained by EveryCalc - Reviewed June 2026

EveryCalc calculators are designed for fast, practical estimates with transparent inputs and no required account. We use plain formulas, visible assumptions, and related tools so visitors can check the result from more than one angle.

Results are informational only. For financial, tax, legal, medical, construction, or other high-impact decisions, verify the output against primary sources or a qualified professional.

Learn more about our review process on the EveryCalc methodology page.

How this calculator works

What this page estimates

This ARM vs Fixed-Rate Mortgage Calculator is built to give a quick, browser-based estimate for arm vs fixed-rate mortgage. Compare an adjustable-rate mortgage to a fixed-rate mortgage over your planned hold period. See intro and post-adjustment payments and which option costs less in total. The inputs stay on the page during normal use, and the result should be treated as an estimate for planning, comparison, or education rather than professional advice.

Calculation approach

The calculator applies the standard relationship implied by the inputs, then formats the answer so it can be checked and reused. For finance tools, the most important step is using consistent units, rates, time periods, and assumptions before comparing the result with another calculator or outside quote.

Example workflow

For example, start with a realistic value you already know, change one input at a time, and watch how the answer moves. That makes it easier to tell whether the result is being driven by the main amount, the rate, the time period, or a unit conversion.

Practical checks

Use current, real-world numbers when the result affects money, health, tax, or legal decisions.
Run a low, base, and high case when the inputs are estimates.
Check the related calculators below when the next decision depends on a different assumption.

How to interpret the arm vs fixed-rate mortgage result

Best use

Use the result as a planning number for comparing payments, rates, returns, tax reserves, or cash-flow choices before you request a quote or make a commitment.

Cross-check

Compare the answer with the contract, lender estimate, tax form, brokerage statement, payroll record, or invoice that will control the real-world outcome.

Watch for

Do not rely on a single optimistic rate, return, or fee assumption. Money pages work best when you run low, base, and high cases and keep professional advice separate from the estimate.

This page belongs to the Finance calculator library, so the answer should be read in the context of the decision you are modeling rather than as a universal rule.

Before relying on this arm vs fixed-rate mortgage estimate

Most calculator mistakes come from the inputs, not the arithmetic. Use this short audit before you reuse the answer in a spreadsheet, quote, application, or important conversation.

Confirm source numbers

Match balances, rates, fees, taxes, income, and payment dates against the lender quote, payroll record, tax form, statement, invoice, or contract.

Separate cash flow from total cost

A lower monthly payment can still cost more over time if fees, interest, taxes, or a longer term are hidden in the structure.

Run conservative cases

Test at least one higher-cost or lower-return case before using the output for a purchase, refinance, investment, loan, or tax decision.

Rerun this page when the rate, price, term, fee, tax rule, income, expense, or expected holding period changes.

How to Use

Enter the loan amount, total term, and the years you actually expect to keep the loan.
Enter the fixed rate quoted to you on the comparable fixed-rate product.
Enter the ARM intro rate, intro years (5/1, 7/1, 10/1), and your expected post-intro rate.
Read the side-by-side total cost. ARM wins clearly if the savings exceed the rate-rise risk you're willing to accept.

Frequently Asked Questions

When is an ARM the better choice?

ARMs win when (1) your hold horizon is shorter than the intro period, (2) you have flexibility to refinance or sell before the rate adjusts, or (3) you can absorb the worst-case payment without strain. They lose when long horizons combine with rising rates.

How conservative should the post-intro rate be?

Test multiple scenarios: today's index + margin (likely), today + 1% (conservative), and the lifetime cap (worst case). If you can't survive the lifetime cap payment without selling, the ARM is too risky for your situation.

Can I refinance an ARM into a fixed?

Yes, anytime — though closing costs apply. Many borrowers take an ARM with the explicit plan to refinance during the intro period, betting that rates will drop or that they'll move first.

How much does the ARM intro discount usually buy you?

Typically 0.25–0.75% lower than the comparable fixed. On a $400k loan that's $60–$180/mo savings during the intro period — material if you'll be in the loan only 5–7 years.