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Gas Mileage Calculator

Miles per gallon, liters per 100 km, and the cost of a trip.

Miles per gallon

25

From these numbers

300 miles on 12 US gallons is 25 MPG.

That is 9.41 L/100 km and 10.63 km/L.

At $3.50 per gallon, the fuel costs $42.00, which is $0.14 per mile.

L/100 km

9.41

km/L

10.63

Trip fuel cost

$42.00

Miles are international miles (1.609344 km) and gallons are US gallons (3.785411784 L). MPG is miles divided by gallons. Liters per 100 km uses those exact factors. A fuel price is optional and is multiplied by the fuel used, then rounded to the cent.

Learn more

How this calculator works and what to know before using it

What this calculator does

Converts a trip's distance and fuel into miles per gallon, liters per 100 km, and the fuel cost.

How to use it

  1. Enter the distance in miles or kilometers.
  2. Enter the fuel in US gallons or liters.
  3. Add a price per gallon or per liter if you want the cost.

Formula used

Miles per gallon

MPG = miles รท US gallons. L/100 km uses 1 mile = 1.609344 km and 1 US gallon = 3.785411784 L. Trip cost is the fuel amount times the price, rounded to the cent.

Source. Miles per gallon is miles divided by US gallons. Liters per 100 km uses 1 mile = 1.609344 km and 1 US gallon = 3.785411784 L. Trip cost is the fuel amount times the price, rounded to the cent. The mile and gallon factors are the exact values in NIST Special Publication 811. NIST Special Publication 811.

Updated November 1, 2026

Example

300 miles on 12 US gallons is 25 MPG. That is 9.41 L/100 km and 10.63 km/L. At $3.50 per gallon, the fuel costs $42.00, which is $0.14 per mile.

Good to know

  • Gallons are US gallons, not imperial gallons.

Common questions

What is the difference between MPG and L/100 km?
MPG rises when the car uses less fuel. L/100 km falls. Both describe the same trip, using exact mile and US-gallon factors.
Can I leave the price blank?
Yes. Mileage is shown either way. The cost appears when a price is entered.

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