The Gas Mileage Calculator works out your car's fuel economy from odometer readings and the fuel added, in mpg or liters per 100 km, plus the cost of driving.
Fuel economy: 24.00 mpg
| Miles per gallon | 24.00 |
| Liters per 100 km | 9.80 |
| Kilometers per liter | 10.20 |
| Distance driven | 360 miles |
| Fuel cost | $45.00 |
| Cost per mile | $0.13 |
Fill the tank completely and note the odometer. Drive normally, fill up again and note the new reading and how much fuel went in. Distance ÷ fuel gives miles per gallon; fuel ÷ distance × 100 gives liters per 100 km.
Worked example (defaults): 12,360 − 12,000 = 360 miles on 15 gallons = 24 mpg, or 9.8 L/100 km. At $3 a gallon that is $45, 12.5 cents a mile.
Keep tires properly inflated, remove roof racks and extra weight, drive smoothly, avoid long idling, keep speeds moderate (fuel economy usually drops above 50–60 mph) and keep up with maintenance.
MPG measures distance per fuel (higher is better); L/100 km measures fuel per distance (lower is better). To convert, L/100 km = 235.215 ÷ mpg (US gallons).
Why is my real mpg lower than the sticker? Official tests use set conditions; weather, traffic and driving style matter.
Should I average several fill-ups? Yes, it gives a more accurate figure.
For trip costs use the Fuel Cost Calculator.