The direct answer: a payday loan is a fixed-fee product, not a variable-rate one. The lender charges a flat finance fee, typically $15 per $100 borrowed, and that fee is written into the agreement before you sign. There is no index, no prime rate, no adjustment clause. Borrow $375 for 14 days and the fee is $56.25. It cannot move.
That sounds reassuring. It shouldn't be. The fee is fixed per term, the term is usually two weeks, and the fee comes due again every time the loan is extended. So the useful question is not whether the rate can change mid-loan, but what happens when the term ends and the balance is still there.
What "Fixed" Legally Means in a Payday Agreement
Under the Truth in Lending Act and its implementing rule, Regulation Z, a payday lender must disclose two numbers in writing before you sign: the finance charge in dollars, and the cost expressed as an annual percentage rate. Both are binding for the term of the agreement. On a 14-day loan priced at $15.00 per $100, the disclosure box will show an APR of roughly 391%, and the lender cannot revise either figure while that term runs.
That is the entire legal content of "fixed" here. It is a promise about one term, not about your total cost of borrowing. The disclosure says nothing about what the loan costs if you cannot repay in full on the due date, which is exactly where most of the expense accumulates.
State law reinforces the flat-fee structure. Most states that permit payday lending regulate the price by capping the fee itself rather than setting an interest ceiling, which is why quotes cluster in a narrow band from $10 to $30 per $100 instead of drifting with the market. A lender in a fee-cap state could not offer you a variable rate even if it wanted to. The statute defines the product as a fee, so the fee is what you get.
Fixed Per Term, Charged Again and Again
A payday loan is repaid in a single balloon payment: principal plus fee, all at once, on your next payday. When a borrower cannot cover that lump sum, states that permit it let the lender "roll over" the loan, extending the due date in exchange for a brand-new fee. The principal does not shrink by a cent.
Run the typical numbers. A $375 loan carries a $56.25 fee. Roll it over three times and you have paid the fee four times, which comes to $225.00 in charges, while still owing the original $375. CFPB research on payday lending found that a large share of loans go to borrowers caught in exactly this re-borrowing sequence.
This is why the fixed label hides more than it reveals. A variable rate drifts by fractions of a percentage point when the market moves. A rollover repeats the entire finance charge. The effective cost of a "fixed" payday fee, held for a few months, behaves worse than almost any variable-rate product a consumer can legally be offered.
Fixed vs. Variable: The Two-Minute Primer
Variable rates move with an index
A variable APR is pegged to a benchmark, almost always the prime rate, which follows the Federal Reserve's target rate. Credit cards are the everyday example: when the Fed moves, card APRs follow within a billing cycle or two. The average assessed purchase APR has sat around 22% recently, per the Federal Reserve's G.19 consumer credit release, with issuers pricing between 18% and 30% depending on credit profile.
Fixed rates stay put for the schedule
An installment loan typically carries one fixed APR for the whole repayment schedule, with every payment reducing principal. Online subprime installment lenders commonly price between 36% and 160% APR; bank and credit-union personal loans run from about 8% to 36%. The payment on the first month equals the payment on the last, which is what most people picture when they hear "fixed."
Fixed or Variable, Product by Product
Here is how the common small-dollar borrowing routes split by rate type, with typical pricing from published rate ranges:
| Product | Rate type | Typical pricing |
|---|---|---|
| Payday loan | Fixed flat fee per term | $15 per $100, about 391% APR |
| Title loan | Fixed monthly fee, re-charged on rollover | 25% monthly, about 300% APR |
| Installment loan | Fixed APR | 36%–160% APR |
| Bank personal loan | Usually fixed APR | 8%–36% APR |
| Credit card | Variable APR, tied to prime | Around 22% average purchase APR |
| Payday Alternative Loan (PAL) | Fixed APR | Capped at 28% APR by NCUA rule |
| Bank overdraft | Fixed fee per item | $27 typical per item |
Notice what actually sorts that table. It is not fixed versus variable that separates the cheap products from the expensive ones. The two entries priced as fixed fees that can be re-charged, payday and title, sit at the top of the cost range, while the only truly variable product lands near the bottom. Repayment structure does the sorting; the rate label is almost decorative.
The Rate Type Matters Less Than the Rate
Fixed versus variable is the wrong axis for judging a payday loan. A variable card APR near 22% drifting a full point changes the cost of carrying $100 by roughly a dollar a year. A fixed payday fee annualises to about 391% from the moment you sign. The label on the rate is stable; the size of it is the problem, and the rollover mechanics multiply it.
If you are weighing an offer, ignore the fixed/variable framing and compare annualised cost across your real options first. Our guide to payday loans online walks through the full pricing structure, and if you have no checking account, read whether a payday loan is possible without a bank account before assuming a storefront is the only route. To see what any quoted fee costs per year, run it through the payday loan calculator.