Fixed vs. Variable Rate Loans

What Is It

A fixed-rate loan keeps the same interest rate for the entire life of the loan — same rate, same payment, from the first month to the last. A variable (or adjustable) rate loan resets periodically to a market index, such as SOFR or the Prime Rate, plus a margin the lender sets when you take out the loan. Per the CFPB, index plus margin becomes your new rate each time it adjusts.

Why It Matters

The real tradeoff is time, not just risk tolerance. A fixed rate protects you from future increases; a variable rate typically starts lower during an introductory period, betting that rates won't climb enough to erase that early head start. For mortgages specifically, adjustable-rate loans commonly come with rate caps limiting how much the rate can move at the first adjustment, at each adjustment after that, and over the life of the loan — but that specific cap structure and disclosure isn't universal across every loan type. Personal loans and private student loans can use the same index-plus-margin mechanic without necessarily carrying the same caps.

Quick Example

A 5/1 ARM — fixed for 5 years, then adjusting annually — starts at a 5% rate with a 2% initial cap, a 2% subsequent cap, and a 5% lifetime cap. Even in the worst case, the rate can't exceed 7% at the first adjustment (5% + 2%), or 10% at any point over the life of the loan (5% + 5%). The exact future rate is genuinely unknown in advance — but the caps put a hard ceiling on how bad the worst case can get.

Try It Yourself

Model the payment at your current rate, then compare it against a higher or lower one.

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