Prime Rate vs Fixed Rate Calculator
Compare the total cost of a variable-rate loan versus a fixed-rate personal loan across nine rate scenarios
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Prime Rate vs Fixed Rate Calculator
Variable vs Fixed: Which Loan Costs Less?
Each card shows the total cost difference between variable and fixed if prime moves by that amount over your loan term. Green = variable wins. Gold = fixed wins.
Variable-rate scenarios assume the rate change occurs gradually (linear) over the loan term. Fixed-rate cost stays constant regardless of prime movement.
Key Takeaways
- At today's 6.75% prime rate, a variable-rate loan at prime + 4% (10.75% APR) currently costs less per month than the average fixed-rate personal loan at 12.26% APR.
- On a $15,000 loan over 36 months, the variable option saves roughly $538 in total interest — but only if prime stays flat or drops.
- The breakeven point is the prime rate increase at which the variable loan becomes more expensive than the fixed alternative. For a typical 36-month loan, that is around a 1.50% prime rate increase.
- Fixed-rate loans provide payment certainty: your monthly amount never changes, making budgeting straightforward regardless of Federal Reserve decisions.
- The scenario grid below the comparison lets you stress-test nine different rate paths from prime dropping 2% to rising 2%.
How to Use This Calculator
This calculator runs a side-by-side comparison between a variable-rate loan tied to the prime rate and a fixed-rate personal loan. It accounts for rate movement over time, not just the starting rate, which makes the comparison more realistic than a simple APR comparison.
Step 1 — Enter your loan amount. Use the input or slider. The default is $15,000, which is close to the national average personal loan balance.
Step 2 — Set your variable-rate margin. This is the percentage your lender adds above prime. Credit cards typically add 12%–18%, HELOCs add 0.5%–3%, and personal lines of credit add 3%–8%. The current APR appears in green below the input.
Step 3 — Enter the fixed rate you qualify for. The default is 12.26%, which is the national average personal loan APR as of March 2026. If you have been pre-qualified at a specific rate, enter that instead for a personalized comparison.
Step 4 — Choose a loan term and rate scenario. The term sets how long you will be exposed to variable rates. The rate scenario models whether prime stays flat, rises, or falls over that period. The calculator assumes the change occurs gradually, not all at once.
Step 5 — Read the verdict and explore scenarios. The green or gold verdict box tells you which option wins under your chosen scenario. The scenario grid at the bottom shows all nine rate paths at once, so you can quickly see where the crossover point is.
Understanding the Results
The core output is the total cost comparison — not just the monthly payment difference, but the cumulative interest over the entire loan term. A variable rate might start lower than a fixed rate, giving it a monthly payment advantage on day one. However, if prime rises during the loan, the variable rate climbs while the fixed rate stays locked. The calculator models this by simulating monthly payments across the full term with the rate changing linearly.
The average APR over term metric is especially useful. It combines the starting rate with the projected ending rate to give you an effective rate for comparison purposes. If the variable loan's average APR ends up higher than the fixed rate, the fixed option wins on total cost even though it started higher.
The scenario grid is where the real decision-making happens. It shows the winner and the dollar savings at each of nine rate paths simultaneously. Most borrowers find a clear pattern: the variable rate wins at flat or declining rates, and the fixed rate wins if prime rises by a certain threshold. That threshold — the breakeven point — is your key decision metric. If you believe prime is likely to rise by more than the breakeven amount during your loan term, the fixed rate is the safer choice.
Variable vs Fixed Rate: Feature Comparison
| Feature | Variable Rate (Prime + Margin) | Fixed Rate |
|---|---|---|
| Starting APR | Often lower (10%–12% typical) | Slightly higher (12%–14% typical) |
| Rate stability | Changes with Fed decisions | Locked for the life of the loan |
| Best when rates are... | Falling or flat | Rising or uncertain |
| Budget predictability | Payment can change each period | Same payment every month |
| Risk | Borrower bears interest rate risk | Lender bears interest rate risk |
| Common products | Credit cards, HELOCs, some personal LOCs | Personal loans, auto loans, most mortgages |
Frequently Asked Questions
Should I choose a variable or fixed rate loan?
It depends on your risk tolerance and rate outlook. If you are comfortable with payment fluctuations and believe rates will stay flat or decline, a variable rate often starts lower and saves money. If you prefer budget certainty and want protection against rate increases, a fixed rate eliminates the guesswork. The scenario grid in the calculator above shows exactly where each option wins for your specific loan.
Can I switch from a variable rate to a fixed rate later?
Yes, through refinancing. If you start with a variable-rate product and rates rise, you can apply for a fixed-rate personal loan to pay off the variable debt. Keep in mind that refinancing may involve a new credit check and potentially an origination fee, so factor those costs into the comparison.
What is the breakeven point for variable vs fixed?
The breakeven is the amount prime would need to rise for the variable loan to cost the same as the fixed loan over the full term. You can find your specific breakeven by scanning the scenario grid in the calculator — it is the point where the cards switch from green (variable wins) to gold (fixed wins).
How does the calculator model rate changes?
The calculator assumes the rate change occurs gradually and evenly over the loan term (linear interpolation). For example, if you select "+1.00%" over 36 months, the variable rate increases by roughly 0.028% per month. This is more realistic than assuming the entire change happens on day one or at a single point in time.
Why is the fixed rate usually higher than the variable starting rate?
Lenders charge a premium for rate certainty. When you lock a fixed rate, the lender accepts the risk that market rates could rise — if they do, the lender earns less than it could have. That risk premium typically adds 1%–3% above the comparable variable rate at origination.
Does this calculator account for origination fees?
No. Both sides of the comparison assume no origination fee, so the total cost reflects interest charges only. If one option has a fee and the other does not, you can add the fee amount to the total cost of that option for a more complete comparison. Our Origination Fee Impact Calculator can help you model this.
References & Further Reading
- Federal Reserve H.15 — Selected Interest Rates
- CFPB — Fixed vs Variable Rate Loans
- FRED — Bank Prime Loan Rate
Keep Reading
- Prime Rate Impact Calculator — See the monthly dollar impact of rate changes
- Prime Rate History & Forecast — 25 years of rate data with loan projector
- Best Personal Loans — Compare fixed-rate offers
- How Loans Affect Your Credit Score
- All PrimeRates Calculators