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MPG Calculator

Calculate Miles Per Gallon (MPG) to evaluate vehicle efficiency and compare US versus UK imperial fuel ratings.

Calculator Inputs

Live
mi
10 mi1,500 mi
gal
1 gal50 gal
Calculation Results
US Miles Per Gallon
35.28 MPG
km per Litre Equivalent
15 km/L
UK Imperial MPG
42.37 MPG
Liters per 100km
6.67 L/100km
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How to use the MPG Calculator

  1. 1Enter total miles driven on a full tank.
  2. 2Enter gallons of fuel required to refill.
  3. 3View US MPG, UK Imperial MPG, and metric equivalents instantly.

How MPG is Calculated

MPG is calculated by dividing total miles driven by the volume of fuel gallons burned.

Mathematical Formula
US MPG = Miles / US Gallons UK MPG = US MPG × 1.20095 km/L = US MPG / 2.35215
Formula Variables & Logic

1 US liquid gallon is 3.785 liters, while 1 UK imperial gallon is 4.546 liters.

Worked Example: Highway Road Test
Sample Calculation
Scenario: A vehicle covers 380 miles on 12.5 US gallons of fuel.
Step-by-step breakdown
  1. 1US MPG = 380 / 12.5 = 30.40 MPG
  2. 2UK Imperial MPG = 30.40 × 1.20095 = 36.51 MPG
  3. 3km/L = 30.40 / 2.35215 = 12.92 km/L
Estimated Result
The vehicle achieved 30.40 US MPG (12.92 km/L).

What affects MPG results

  • Difference between US and UK imperial gallon units.
  • Ethanol blend in gasoline (E10 or E15 yields slightly lower MPG than pure gasoline).
  • Aerodynamic drag from highway speeds.
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Frequently Asked Questions

Why is UK MPG higher than US MPG for the same car?

The UK imperial gallon is roughly 20% larger (4.546 L) than the US liquid gallon (3.785 L), so a car travels more miles per imperial gallon.

What is considered good MPG today?

For non-hybrid petrol cars, 30+ MPG is good; hybrid vehicles typically achieve 45 to 55+ MPG.

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