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Gas Mileage Calculator

Track fuel economy (MPG & L/100km) and analyze your fuel costs over distance.

Input Log

Please enter a valid distance and fuel amount to generate results.

Tip: Keep tires properly inflated and avoid carrying unnecessary cargo to improve your MPG by up to 3%.

Efficiency Science

Understanding
Fuel Economy

Fuel economy refers to the relationship between the distance traveled by a vehicle and the amount of fuel consumed. Tracking your fuel economy helps monitor vehicle health, plan travel expenses, and reduce environmental impact.

MPG Metric

Miles per gallon is standard in the US and UK. Note that Imperial (UK) gallons are slightly larger than US gallons.

L/100km Scale

Commonly used in European and metric systems. Unlike MPG, a lower number signifies superior fuel economy.

Driving Habits

Gradual accelerations, proper tire pressure, and limited idling are highly effective in maximizing fuel ranges.

The Formula for Gas Mileage

Calculating your vehicle's fuel efficiency is straightforward if you keep track of your distance and fuel usage:

MPG = Miles Traveled / Gallons of Fuel Used
L/100km = (Liters of Fuel Used / Kilometers Traveled) * 100

Odometer Test Steps:

  • • Fill Tank: Fill your tank to full capacity and reset the trip odometer.
  • • Drive Normally: Drive standard routes until your tank is at least half empty.
  • • Refill & Calculate: Refill to full, write down the miles driven and exact fuel volume added.

How the calculation works

Miles per gallon is distance divided by fuel used.

MPG = miles ÷ gallons L/100km = liters ÷ kilometers × 100

The two units run in opposite directions. Higher MPG is better. Lower L/100km is better.

Worked example: 300 miles on 10 gallons

  1. MPG = 300 ÷ 10 = 30.
  2. The metric cousin of 30 mpg is about 7.84 L/100km, because 235.2 ÷ 30 ≈ 7.84.

Mileage

TripMPG
300 mi / 10 gal30
240 mi / 8 gal30
100 mi / 5 gal20

Frequently asked questions

What MPG is 300 miles on 10 gallons?▼
30.
What is 30 mpg in L/100km?▼
About 7.84.
Which number is better, a higher MPG or a higher L/100km?▼
A higher MPG is better. A lower L/100km is better.