How to Convert MPG to L/100 km Without Reversing the Answer

Miles per gallon tells you how far a vehicle travels on a fixed amount of fuel. Liters per 100 kilometers tells you how much fuel it uses to cover a fixed distance. Higher MPG is better, but lower L/100 km is better: that opposite direction is the source of many comparison mistakes.

The US-gallon formula

For US MPG, divide 235.2146 by the MPG value to estimate L/100 km. A car rated at 30 US MPG uses approximately 235.2146 ÷ 30 = 7.84 L/100 km. To go back, divide 235.2146 by the L/100 km figure. The formula is reciprocal, not a constant multiplier.

Check which gallon is used

An Imperial gallon holds more fuel than a US gallon, so 30 Imperial MPG does not describe the same consumption as 30 US MPG. For Imperial MPG, the conversion constant is about 282.481 instead of 235.2146. Always identify the market and the gallon type before comparing two vehicle specifications.

What a rating cannot promise

Official fuel-consumption tests follow standard cycles. Your actual result can change with traffic, weather, load, tire pressure, and driving style. Convert published ratings to compare like with like, then use real driving data to estimate your own fuel costs.

• 30 US MPG is about 7.84 L/100 km.
• 40 US MPG is about 5.88 L/100 km.
• 5 L/100 km is about 47.04 US MPG.