Mileage Calculator

Your Actual Mileage, Not the Sticker Number

EPA window-sticker ratings are a lab estimate; the number that matters for your budget is what your vehicle actually returns between fill-ups, which shifts with driving style, terrain, and season. Logging distance traveled against fuel used at each fill-up turns that variability into a real, trackable figure instead of a guess.

The Formula

Imperial: MPG = Distance (miles) ÷ Fuel Used (gallons)
Metric: L/100km = (Fuel Used (liters) ÷ Distance (km)) × 100

The calculator also converts the result across MPG, L/100km, and km/L automatically, since L/100km is an inverse measure — a lower number means better efficiency, the opposite of MPG.

Where This Matters

Tracking efficiency over time — logging MPG at every fill-up flags a gradual drop that often signals a maintenance issue (tire pressure, air filter, worn spark plugs) before it becomes expensive.
Verifying advertised figures — comparing your logged MPG against the EPA rating shows how much your actual driving conditions deviate from the lab test.
City vs. highway comparison — running separate calculations for a highway-heavy tank versus a stop-and-go tank isolates how much driving style affects consumption.
Cross-border unit conversion — travelers switching between US MPG and metric L/100km figures get a direct, correct conversion rather than a rough mental estimate.

MPG to L/100km Reference

Common MPG (US) values converted to L/100km
MPG (US)	L/100km
15	15.7
20	11.8
25	9.4
30	7.8
35	6.7
40	5.9
50	4.7
60	3.9

Conversion uses the constant 235.214583, the standard factor for MPG (US) ↔ L/100km.

How to Use This Calculator

Choose Imperial (miles, gallons) or Metric (km, liters).
Enter the distance traveled since your last fill-up.
Enter the fuel used to cover that distance.
Select Calculate to get your MPG or L/100km, plus the equivalent in the other common units.

Related Calculations

Turn your logged mileage into a trip budget with the Fuel Cost Calculator, or convert between fuel economy units directly using the Fuel Economy Calculator.