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Fuel Economy Converter

Convert between MPG (US), MPG (UK), liters per 100 km, km per liter, and miles per liter.

About this Calculator

Convert between MPG (US), MPG (UK), liters per 100 km, km per liter, and miles per liter.

Formula & Calculations

Formula

Conversions use defined relationships: 1 US gallon = 3.78541 L, 1 UK gallon = 4.54609 L, 1 mile = 1.60934 km
Where:
  • MPG (US)=Miles per US gallon
  • MPG (UK)=Miles per Imperial UK gallon (1 UK gal = 4.54609 L)
  • L/100km=Liters per 100 kilometers (common in Europe and Asia)
  • km/L=Kilometers per liter
  • mi/L=Miles per liter

Assumptions

  • MPG (US) uses the US gallon of 3.78541 liters.
  • MPG (UK) uses the Imperial gallon of 4.54609 liters.
  • 1 mile = 1.60934 kilometers.

Calculation Examples

Example 1

Inputs:30 MPG (US) to L/100km
Result:7.84 L/100km

235.215 ÷ 30 = 7.84 L/100 km.

Example 2

Inputs:40 MPG (UK) to MPG (US)
Result:33.31 MPG (US)

40 × 3.78541 ÷ 4.54609 = 33.31 MPG (US).

Example 3

Inputs:6 L/100km to MPG (US)
Result:39.2 MPG (US)

235.215 ÷ 6 = 39.2 MPG (US).

Frequently Asked Questions

Why is UK MPG different from US MPG?

The UK Imperial gallon is about 4.546 liters, while the US gallon is about 3.785 liters. This means a UK gallon is roughly 20% larger, so UK MPG numbers appear higher for the same fuel efficiency.

How do I convert between L/100km and MPG?

Use the formula: MPG (US) = 235.215 ÷ L/100km, or L/100km = 235.215 ÷ MPG (US). For UK MPG, use 282.481 instead of 235.215.