Automotive Fuel Economy & Math Guides
In-depth, human-written technical guides detailing the math, physics, testing procedures, and conversion formulas for vehicle fuel economy and road trip budgeting.
How to Calculate Fuel Consumption
Fuel consumption measures the volume of fuel a vehicle uses to travel a specific distance. In the metric system, it is commonly expressed in liters per 100 kilometers (L/100km) or kilometers per liter (km/L). In the United States, it is expressed as miles per gallon (MPG).
How to Calculate Gas Mileage
Gas mileage measures how many miles a vehicle travels per gallon of gasoline consumed. In the United States, gas mileage is expressed as miles per gallon (MPG). To calculate your gas mileage, divide the miles driven by the US gallons of fuel used (MPG = Miles Driven ÷ Gallons Used). Because a UK Imperial gallon is approximately 20% larger than a US gallon, UK Imperial MPG figures are numerically higher for the exact same vehicle.
How to Calculate Fuel Cost
Fuel expenses represent one of the largest ongoing operational costs of vehicle ownership. Calculating your cost per mile and trip costs enables accurate tax deductions, road trip cost sharing, and smart commuter budgeting.
How to Calculate MPG (Miles Per Gallon)
Miles Per Gallon (MPG) is the standard measurement of vehicle fuel economy in the United States and the United Kingdom. Here is the exact math behind MPG calculations and unit comparisons.
How to Calculate Fuel Consumption From a Full Tank
The full-tank odometer method is the universally recognized scientific standard for measuring passenger vehicle fuel consumption without specialized laboratory telemetry.
MPG vs km/L: Conversion & Differences
Both MPG and km/L measure distance per unit of fuel. Converting between them requires accounting for the exact ratio between miles and kilometers, and gallons and liters.
US MPG vs UK MPG: What Is the Difference?
When reading British automotive publications like Top Gear or Autocar, you may notice vehicles achieving seemingly incredible fuel economy. This difference is caused by the physical volume of the British Imperial gallon.
L/100km vs MPG: Inverse Scales & The MPG Illusion
L/100km and MPG are inverse metrics. One measures fuel consumption (volume per distance), while the other measures fuel economy (distance per volume). This difference creates a well-documented cognitive bias known as the MPG Illusion.
How to Measure Real-World Fuel Economy
Sticker fuel economy ratings are conducted in laboratory dyno cells. Real-world fuel economy is influenced by ambient weather, altitude, road grades, payload, and driving habits. Here is how to measure your true baseline.