To calculate MPG, divide the miles you drove by the gallons you used — for example 320 miles ÷ 11.5 gallons = 27.8 MPG. Fuel cost per mile is gas price ÷ MPG, so a 24-mpg car at $3.50/gal costs about $0.15/mile. A good MPG is anything above the ~24 mpg average of a new car; hybrids clear 45–57 mpg. Use the calculator above for your exact numbers.
How to calculate MPG
MPG (miles per gallon) is miles driven ÷ gallons of fuel used. To measure your real-world number:
- Fill up completely and reset your trip odometer (or note the reading).
- Drive normally until you're ready to refuel — more miles = more accurate.
- Fill up again and note the gallons the pump added and the miles since the last fill.
- Divide miles by gallons — that's your real MPG. The calculator above does it instantly, with your cost.
Example: 320 miles on 11.5 gallons = 27.8 MPG. Real-world MPG usually runs a bit below the EPA sticker — this shows what you actually get.
Fuel cost by MPG — per year
What a year of driving costs at each MPG level (15,000 miles a year, $3.50/gal), and what you'd save versus a typical 24-mpg car — a quick reference before you plug in your own numbers:
| MPG | Fuel / year | Fuel / month | vs 24-mpg car |
|---|---|---|---|
| 15 mpg | $3,500 | $292 | +$1,313 |
| 18 mpg | $2,917 | $243 | +$729 |
| 20 mpg | $2,625 | $219 | +$438 |
| 22 mpg | $2,386 | $199 | +$199 |
| 25 mpg | $2,100 | $175 | −$88 |
| 28 mpg | $1,875 | $156 | −$313 |
| 30 mpg | $1,750 | $146 | −$438 |
| 35 mpg | $1,500 | $125 | −$688 |
| 40 mpg | $1,313 | $109 | −$875 |
| 45 mpg | $1,167 | $97 | −$1,021 |
| 50 mpg | $1,050 | $88 | −$1,138 |
Going from 24 to 40 mpg saves roughly $875/year at these assumptions. Change the gas price and mileage in the calculator above for your own figures.
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Cheapest cars to fuel right now
The 2026 models with the lowest annual fuel cost (EPA estimate at ~15,000 mi/yr) — what the calculator would show for a full year of driving each:
| # | Car | Annual fuel | Combined MPG |
|---|---|---|---|
| 1 | Toyota Prius | 57 mpg | |
| 2 | Hyundai Elantra | 54 mpg | |
| 3 | Kia Niro | 53 mpg | |
| 4 | Toyota Camry | 51 mpg | |
| 5 | Hyundai Sonata | 51 mpg | |
| 6 | Honda Civic | 49 mpg | |
| 7 | Toyota Corolla | 50 mpg | |
| 8 | Honda Accord | 48 mpg | |
| 9 | Honda Prelude | 44 mpg | |
| 10 | Lexus UX | 43 mpg |
See the full best MPG ranking, by type (SUVs, hybrids), or the most efficient cars under $25k.
Is your MPG good?
The average new car in 2026 gets about 24 mpg combined. Above that beats the pack; hybrids clear 45–57 mpg. See what's a good MPG by car type. The most fuel-efficient new cars right now:
- Toyota Prius — 57 mpg combined
- Hyundai Elantra — 54 mpg combined
- Kia Niro — 53 mpg combined
- Hyundai Sonata — 51 mpg combined
- Toyota Camry — 51 mpg combined
MPG conversions
US MPG converts to the metric and UK figures like this — divide 235.21 by your MPG for L/100km, or multiply by 1.201 for UK (imperial) MPG:
| US MPG | L/100km | km/L | UK MPG |
|---|---|---|---|
| 20 US mpg | 11.8 L/100km | 8.5 km/L | 24.0 UK mpg |
| 25 US mpg | 9.4 L/100km | 10.6 km/L | 30.0 UK mpg |
| 30 US mpg | 7.8 L/100km | 12.8 km/L | 36.0 UK mpg |
| 35 US mpg | 6.7 L/100km | 14.9 km/L | 42.0 UK mpg |
| 40 US mpg | 5.9 L/100km | 17.0 km/L | 48.0 UK mpg |
| 45 US mpg | 5.2 L/100km | 19.1 km/L | 54.0 UK mpg |
| 50 US mpg | 4.7 L/100km | 21.3 km/L | 60.0 UK mpg |
MPG calculator — FAQ
How do I calculate MPG?
Divide the miles you drove by the gallons of fuel you used: MPG = miles ÷ gallons. Fill up, drive, fill up again, then divide the miles since the last fill by the gallons it took.
What is a good MPG?
Above the ~24 mpg average of a new car is good; 40+ mpg is excellent and usually means a hybrid. SUVs and trucks average lower — see best MPG by class.
Why is my real MPG lower than the EPA rating?
EPA numbers come from standardized lab tests. Real driving — cold starts, traffic, speed, AC, cargo and terrain — usually lands a few MPG below the sticker. This calculator shows your actual mileage.
How do I calculate fuel cost?
Cost per mile = gas price ÷ MPG. For a trip, multiply by the distance; for a year, by your annual miles. The calculator does all three once you add a gas price.
How do I convert MPG to L/100km?
Divide 235.21 by your MPG — e.g. 30 MPG ≈ 7.8 L/100km.