Car Comparison Calculator
See which of two cars actually costs less to run
Two cars can look almost identical on paper — similar price, similar size, similar features — and still cost very different amounts to actually drive. The gap almost always comes down to one number most buyers skim past: fuel economy. Our car comparison calculator above puts that number to work, showing you exactly how much more (or less) any two vehicles will cost you over the same distance.
Whether you’re choosing between a compact sedan and a crossover, weighing a hybrid against its gas-only twin, or just seeing how your current car stacks up against one you’re considering, this tool turns a vague “it probably gets better gas mileage” into an actual dollar figure.
Table of Contents
How to Compare Two Cars
- Set your comparison distance — this could be your average monthly driving distance, a typical road trip, or any distance you want the comparison based on.
- Name both vehicles — enter the make and model (or just “Car A” and “Car B”) so the result is easy to read.
- Enter each vehicle’s fuel economy — the combined MPG from the window sticker, from fueleconomy.gov, or a real-world figure if you track your own mileage.
- Enter your gas price and currency — the same price is applied to both cars for a fair comparison.
The calculator instantly tells you which car is cheaper to run, by how much, and projects that saving over multiple trips — so a small per-trip difference turns into a real annual figure.
Why a Few MPG Makes a Bigger Difference Than You’d Think
A gap that looks tiny on the sticker compounds fast. Consider two cars covering 1,000 miles a month:
- Car A: 25 MPG → uses 40 gallons
- Car B: 35 MPG → uses 28.6 gallons
At $3.10 a gallon, that’s a monthly difference of about $35 — over $420 a year — from the MPG gap alone, before accounting for any difference in purchase price, insurance, or maintenance.
This is exactly why careful buyers look past the sticker price. A car that costs a little more up front but gets significantly better mileage often works out cheaper across a typical five-year ownership period.
What This Calculator Doesn’t Include (and Why That’s Okay)
This tool focuses specifically on fuel cost — it doesn’t factor in purchase price, insurance, depreciation, or maintenance, because those vary too much by model, trim, and state to estimate reliably. Think of it as one clear input into a bigger buying decision, not the whole picture. Pair the fuel cost comparison with our buying guides for a fuller before-you-buy checklist.
EPA Ratings vs. Real-World MPG
One thing to keep in mind when comparing cars: the MPG figures on a window sticker come from standardized EPA test cycles, and real-world driving — traffic, air conditioning, short trips, aggressive acceleration, cold weather — typically brings that number down. For a fair comparison, try to use real-world numbers for both cars (owner-reported data on fueleconomy.gov is a good source) rather than the sticker figure, since the gap between tested and real-world economy isn’t the same for every model.
Gas vs. Hybrid vs. Diesel: A Quick Note
If you’re comparing across fuel types rather than two gas cars, enter the correct price for each fuel — diesel and regular gas are priced differently, and premium-required models cost more per gallon than their EPA numbers alone suggest. Hybrids report a combined MPG that already accounts for their electric assist, so you can enter that figure directly. For cross-fuel comparisons, run the calculation once per fuel price and compare the two results.
Frequently Asked Questions
Can I compare a gas car with a diesel or premium-fuel car?
Yes. Just make sure you use the correct price per gallon for each vehicle — the calculator applies one price field at a time, so for cross-fuel comparisons, run it once per fuel type and compare the two results.
What distance should I use for a fair comparison?
Use a distance that reflects your actual driving. Your average monthly mileage is usually more useful than a one-off trip distance, since it better represents real ownership cost. The average American drives roughly 1,100 miles a month.
Does this work for electric vehicles?
This calculator is built around gallons and liters of liquid fuel, so it’s best suited to gas, diesel, and hybrid vehicles. EVs are priced per kWh rather than per gallon, which the tool doesn’t cover.
How accurate are the savings estimates?
The savings figure is only as accurate as the MPG numbers you enter. Using real-world economy rather than sticker figures will give you a more realistic comparison.
Can I use this before test-driving a car?
Absolutely — many buyers use it exactly this way, comparing their current car against a shortlist before deciding which one to go see in person.
Related Tools
- Fuel Cost Calculator — work out the cost of a single trip, split between passengers.
- Commute Cost Calculator — see what either car would cost you monthly and yearly on your actual daily commute.
Make Your Next Car Decision With the Full Picture
Sticker price tells you what a car costs to buy. This calculator tells you what it costs to actually drive. Use it alongside our car reviews and buying guides to see the complete cost of ownership before you sign anything.
