Fuel Economy Calculator
Calculate fuel economy and trip fuel cost from miles and US gallons.
Calculate measured fuel economy
Fuel economy
- Liters per 100 km
- 7.84 L/100 km
- Gallons per 100 miles
- 3.33 gal/100 mi
- Trip fuel cost
- $35.00
- Cost per mile
- $0.12
Measured economy for the distance and fuel you entered, not an EPA rating. A single tank is a small sample.
Your entries and results stay in this browser. This tool does not send, save, or add them to the page address.
Calculate measured fuel economy
Enter miles driven, US gallons used, and the price per gallon. For a tank-to-tank estimate, refill to a consistent level and use the miles traveled since the previous fill.
Formulas
MPG equals miles divided by US gallons. Gallons per 100 miles equals 100 divided by MPG. L/100 km equals approximately 235.2146 divided by US MPG. Trip cost equals gallons multiplied by price.
Measurement limitations
One short trip may not represent typical efficiency. Weather, terrain, traffic, idling, towing, tire pressure, driving style, and refueling consistency affect observed results. This is your measured economy for the distance and fuel you entered, not an EPA rating or a manufacturer estimate, and the two will usually differ.
Frequently asked questions
Does MPG use US or imperial gallons?
This calculator uses US liquid gallons. Imperial gallons are larger and produce a different MPG figure.
How is L/100 km calculated from US MPG?
The calculator divides approximately 235.2146 by US MPG. That constant is 100 kilometers converted to miles and multiplied by the liters in a US gallon. Lower L/100 km means less fuel used for the same distance.
Why might dashboard fuel economy differ?
Refueling level, odometer accuracy, tire size, idling, driving conditions, and vehicle estimates can all affect the result.
Are taxes included in fuel cost?
Use the complete per-gallon price paid. The calculator multiplies gallons used by that price and adds no separate taxes or fees.