ToolGrym field guide
How ARM Rate Adjustments Work
ARM adjustments follow contract terms: an index, a margin, an adjustment interval, and caps. Understanding each piece makes the payment risk measurable.
- Format
- Plain-English explainer
- Practice
- 3 linked calculators
Written by the ToolGrym Editorial Team
Last reviewed:
Fully indexed rate
At a reset, the contract generally adds a fixed margin to a published index, then applies caps and floors. The rate is not simply whatever the lender wants to charge.
Payment is a separate calculation
The new rate is applied to the remaining balance and remaining term. That means the payment can rise even if the rate change appears modest. Use the ARM stress test and ask the lender for the maximum payment disclosure.
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