ARM Mortgage Calculator

Calculate adjustable-rate mortgage payments with rate caps. See worst-case scenario vs fixed rate.
$
%
Initial Period
%
%
%
%
%

Initial Payment

$2,271.16

Worst-Case Payment

$3,491.98

30yr Fixed Payment

$2,594.39

ARM vs Fixed Comparison

Initial ARM Payment$2,271.16
30yr Fixed Payment$2,594.39
Monthly Savings (first 5 yrs)$323.24
Total Savings (first 5 yrs)$19,394.18
First Adjustment Rate7.25%
First Adjustment Payment$2,673.25
Worst Case Rate (lifetime cap)10.50%
Worst Case Payment$3,491.98

Rate Adjustment Schedule

Initial (Years 1-5)$2,271.16
Year 6 — 7.25%$2,673.25
Year 7 — 7.25%$2,713.18
Year 8 — 7.25%$2,757.47
Year 9 — 7.25%$2,806.71
Year 10 — 7.25%$2,861.64

Use the ARM Mortgage Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

An Adjustable-Rate Mortgage (ARM) calculator helps you understand how your mortgage payments might change over time due to fluctuating interest rates. This is crucial for budgeting and assessing the long-term affordability and risk associated with an ARM.

The calculator first determines the initial fixed-rate payment using standard amortization formulas. After the fixed-rate period, it recalculates payments at specified intervals based on a new interest rate (index + margin), often adhering to periodic and lifetime caps.

A common mistake is underestimating the impact of rising interest rates, especially when ignoring lifetime caps. Always factor in potential payment increases to ensure you can afford the mortgage even during unfavorable market conditions.

Example: ARM Payment Adjustment

  1. 1 Imagine a $300,000 mortgage with an initial 5% interest rate for 5 years (5/1 ARM). After 5 years, the index is 3% and the margin is 2%, resulting in a new rate of 5%.
  2. 2 Initial payment for a 30-year term at 5% would be approximately $1,610.46. After 5 years, with the new rate still at 5% (due to index + margin), and a remaining principal of about $276,432 over 25 years, the payment would remain very similar.
  3. 3 Initial monthly payment: ~$1,610.46. After 5 years, if the rate adjusts to 5%, the new monthly payment would be approximately $1,618.00.
  4. 4 In this scenario, the rate didn't change significantly, leading to a minor payment increase. This highlights the importance of understanding how index and margin combine to determine your new rate, and how even small changes can impact your budget.

Source: CFPB — Owning a Home · Last updated: April 2026

Frequently Asked Questions

How does an adjustable rate mortgage work?
An ARM has a fixed rate for an initial period (typically 5, 7, or 10 years), then adjusts annually based on a benchmark index plus a margin. A 5/1 ARM is fixed for 5 years, then adjusts every 1 year. Initial ARM rates are typically 0.5-1.5% lower than fixed rates.
What are ARM rate caps?
ARMs have three caps: initial adjustment cap (how much the rate can change at first adjustment, typically 2%), periodic cap (maximum change per adjustment period, typically 2%), and lifetime cap (maximum total increase, typically 5%). A 5/1 ARM starting at 5.5% with a 5% lifetime cap cannot exceed 10.5%.
When does an ARM make sense over a fixed rate?
An ARM makes sense if you plan to sell or refinance before the fixed period ends, or if ARM rates are significantly lower than fixed rates. If you will stay in the home long-term through rate adjustments, a fixed rate provides more predictable payments.

You might also need

Mortgage Calculator 2026 — Payment, Amortization & PMI

Calculate your monthly mortgage payment with taxes, insurance, PMI, and HOA. View full amortization schedule. Free, instant results based on current rates.

FHA Loan Calculator 2026 — MIP, Down Payment & Limits

Calculate FHA loan payments including upfront MIP (1.75%) and annual MIP premiums. See when MIP drops off. Free, instant results based on 2026 FHA limits.

Home Affordability Calculator — How Much House Can You Afford?

Find out how much house you can afford based on income, debts, down payment, and current mortgage rates. Free, instant results with DTI ratio breakdown.