Fixed vs Variable Rate: Side by Side
This calculator places fixed-rate and variable-rate student loan scenarios in parallel columns so you can see how total cost diverges if rates move. Enter your balance, both rate offers, and a scenario where the variable rises to a level you choose. On a $55,000 balance, a variable that climbs two points can end up costing more than the fixed offer.
In this scenario you save
Difference between the two
by taking the variable rate — even after it rises to in .
by taking the fixed rate. The rise you modelled wipes out the variable loan's head start.
The two land within a dollar of each other on these numbers.
- Over FixedVariable
- Payment at the start
- Payment after the rise
- Interest paid
- Total paid
The variable loan stops being the cheaper one once the rate climbs past at that same month.
The variable loan is modelled the way lenders handle a rate change: the remaining balance is re-amortised over the remaining term at the new rate, so the payment jumps by . Real variable rates move more than once and have their own caps — check the loan agreement.
How Variable Rates Move
Private student loan variable rates are typically benchmarked to SOFR (the Secured Overnight Financing Rate) plus a lender-set margin. When SOFR rises, your rate and monthly payment rise with it; when SOFR falls, they fall. Most private lenders impose a rate ceiling, but that ceiling can be well above the starting rate.
The appeal of a variable rate is the discount at signing. If a lender offers an illustrative 4.8% variable versus 5.9% fixed on a $55,000 balance, the monthly savings at the start are real—roughly $30 per month (illustrative). But if the variable rate rises to 6.8% over three years, you are now paying more than the fixed offer would have charged. The calculator lets you define the "rises to" scenario so you can see where the crossover falls in months and dollars. Borrowers who plan to pay off the loan within three to five years often benefit from the variable discount; those on longer horizons face more exposure to rate increases.
When Fixed Costs More but Wins
Fixed rates carry a premium because they transfer the interest-rate risk from you to the lender. You pay a higher starting rate in exchange for certainty: the payment on month one is the payment on month one hundred twenty. That premium feels expensive when rates are stable or falling, but it acts as insurance when rates rise sharply.
The calculator quantifies this insurance cost. It shows the difference in total interest between the fixed scenario and the variable scenario at its final rate. If that difference is small—say a few hundred dollars on a $55,000 loan—the peace of mind may be worth the price. If the difference runs into thousands, the variable rate needs to climb significantly before fixed becomes the better deal. There is no universal right answer; the question is how much rate uncertainty your budget can absorb. For a broader refinancing analysis that includes closing costs and break-even timing, see the refinance break-even calculator.
All rates shown are illustrative. Variable rates depend on SOFR plus lender margin and are subject to lender terms. This is not a rate offer.
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Sources
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Sources: credible.com 2026 rate-band survey (Earnest, SoFi ranges); SOFR benchmark (newyorkfed.org); standard amortization math.
- Federal Direct Consolidation Loan interest rate — the weighted average of the loans being consolidated, rounded up to the nearest one-eighth of one percent (Federal Student Aid, studentaid.gov, Loan Consolidation).
- Amortisation, daily interest accrual and payoff arithmetic — standard loan mathematics; every figure on this page is computed from the numbers you enter.