Fixed vs Adjustable Mortgage Rates — Trade-offs

Published May 1, 2026

A fixed-rate mortgage locks the interest rate for the life of the loan (or a long fixed window). An ARM (adjustable-rate mortgage) starts with a teaser rate, then floats with an index plus a margin.

How to choose

Pick fixed when you value predictable payments, plan to stay many years, or rates are historically low.
Consider ARM when you will sell or refinance before the first reset, or when the spread vs fixed is large enough to self-insure future hikes.

What this site’s calculators assume

Our Mortgage Calculator models level principal-and-interest on a fixed rate. For ARMs, rerun whenever the index changes — we do not embed lender margin caps.

Stress test

Add +2% to the rate and see if the payment still fits your budget; if not, avoid ARM exposure or build a larger cash buffer.

How to choose

Pick fixed when you value predictable payments, plan to stay many years, or rates are historically low.
Consider ARM when you will sell or refinance before the first reset, or when the spread vs fixed is large enough to self-insure future hikes.

What this site’s calculators assume

Our Mortgage Calculator models level principal-and-interest on a fixed rate. For ARMs, rerun whenever the index changes — we do not embed lender margin caps.

Stress test

Add +2% to the rate and see if the payment still fits your budget; if not, avoid ARM exposure or build a larger cash buffer.