MPG / Fuel Economy Calculator
MPG / Fuel Economy Calculator
Enter the distance you traveled and the fuel you used, then choose which measurement system to calculate in — MPG (US), liters per 100km, or kilometers per liter. This gives you your vehicle's fuel economy in that system.
The three systems run in opposite directions from each other, which trips people up when comparing figures across regions: for MPG and km/L, a higher number means better efficiency, while for L/100km — the standard used across most of Europe — a lower number is better, since it directly measures how much fuel is consumed over a fixed distance rather than how far a fixed amount of fuel goes. Tracking your own MPG or L/100km over time (using odometer readings and fuel receipts) is also one of the simplest ways to spot a developing mechanical issue, since a sudden drop in efficiency often shows up before other symptoms do.
- MPG formula: Miles Per Gallon = Distance (miles) ÷ Fuel Used (gallons) — higher is more efficient.
- L/100km formula: Liters Per 100km = (Fuel Used in Liters ÷ Distance in km) × 100 — lower is more efficient (opposite direction from MPG).
- km/L formula: Kilometers Per Liter = Distance (km) ÷ Fuel Used (Liters) — higher is more efficient, like MPG.
Why does a lower number mean better efficiency for L/100km but not for MPG?
MPG and km/L measure distance per unit of fuel (more is better), while L/100km measures fuel per unit of distance (less is better) — they're inverse framings of the same underlying efficiency.
How do I convert between these systems directly?
Run the calculation once in your source system, then re-enter the same trip's distance and fuel converted to the target system's units — this calculator handles the formula for whichever system you select.
MPG / Fuel Economy Calculator
Enter the distance you traveled and the fuel you used, then choose which measurement system to calculate in — MPG (US), liters per 100km, or kilometers per liter. This gives you your vehicle's fuel economy in that system.
The three systems run in opposite directions from each other, which trips people up when comparing figures across regions: for MPG and km/L, a higher number means better efficiency, while for L/100km — the standard used across most of Europe — a lower number is better, since it directly measures how much fuel is consumed over a fixed distance rather than how far a fixed amount of fuel goes. Tracking your own MPG or L/100km over time (using odometer readings and fuel receipts) is also one of the simplest ways to spot a developing mechanical issue, since a sudden drop in efficiency often shows up before other symptoms do.
- MPG formula: Miles Per Gallon = Distance (miles) ÷ Fuel Used (gallons) — higher is more efficient.
- L/100km formula: Liters Per 100km = (Fuel Used in Liters ÷ Distance in km) × 100 — lower is more efficient (opposite direction from MPG).
- km/L formula: Kilometers Per Liter = Distance (km) ÷ Fuel Used (Liters) — higher is more efficient, like MPG.
Why does a lower number mean better efficiency for L/100km but not for MPG?
MPG and km/L measure distance per unit of fuel (more is better), while L/100km measures fuel per unit of distance (less is better) — they're inverse framings of the same underlying efficiency.
How do I convert between these systems directly?
Run the calculation once in your source system, then re-enter the same trip's distance and fuel converted to the target system's units — this calculator handles the formula for whichever system you select.