ARM Calculator
Calculate your adjustable-rate mortgage payments with precision
Understand how your adjustable-rate mortgage payment will change when rates adjust after the initial fixed period ends. Model different rate scenarios, caps, and lifetime limits to see worst-case payments across 3/1, 5/1, 7/1, and 10/1 ARM structures.
Basic Loan Information
ARM Adjustment Details
Federal Reserve Bank of St. Louis (FRED) - 1-Year Treasury Rate: (Index %)
Visit: https://fred.stlouisfed.org/series/DGS1
In the top-left corner, under "Observations," you'll see the current index rate.
Once you find the current index rate, enter it in the Index (%) field below in the "Margin + Index = Interest Rate" section.
Visit: https://fred.stlouisfed.org/series/DGS1
In the top-left corner, under "Observations," you'll see the current index rate.
Once you find the current index rate, enter it in the Index (%) field below in the "Margin + Index = Interest Rate" section.
Note: This calculator works for FHA, VA, and conventional ARMs. After the initial fixed period ends, the rate will adjust annually based on your loan's index and margin. Use your loan's specific index rate in the fields below. The calculation boxes are for illustration purposes. You can edit any field to explore different scenarios, and the totals will automatically update.
Margin + Index = Interest Rate
Current Interest Rate + Annual Cap = Interest Rate
+
=
Example: If initial rate is 6.5% and lifetime cap is 5%, the maximum rate is 11.5%
Optional Settings
Interest-Only Period Duration
Enter number of years for interest-only period
Note: During the interest-only period, you'll pay only the interest on the loan each month. Principal payments will begin after this period ends.
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