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

The UK (imperial) gallon is larger than the US gallon — 4.54609 L vs 3.785411784 L. So a car traveling the same distance uses fewer UK gallons, giving a higher MPG figure. A car rated 40 MPG (US) is rated about 48 MPG (UK) for the same real-world efficiency.

What is the exact conversion factor from US MPG to UK MPG?

Multiply US MPG by 1.20095042 (= 4.54609 / 3.785411784). For example, 30 MPG (US) × 1.20095 = 36.03 MPG (UK).

How do I convert UK MPG to US MPG?

Divide UK MPG by 1.20095042 (or multiply by 0.83267). For example, 50 MPG (UK) ÷ 1.20095 = 41.63 MPG (US).

Is US MPG the same as Canadian MPG?

Yes — Canada uses US gallons for MPG figures in informal use, though official Canadian ratings are published in L/100 km. This converter handles US vs UK (imperial) gallons only.

How does MPG relate to L/100 km?

To convert US MPG to L/100 km, divide 235.215 by the US MPG value. To convert UK MPG to L/100 km, divide 282.481 by the UK MPG value.

MPG (US) to MPG (UK) Converter

Name: MPG (US) to MPG (UK) Converter
Availability: InStock
Author: Nham Vu

Enter US MPG to get the UK (imperial) MPG equivalent instantly, with a reverse converter and reference table included.

Converter

US MPG (miles per US gallon)

= — MPG (UK)

UK MPG (miles per imperial gallon) — reverse

= — MPG (US)

1 MPG (US) = 1.20095042 MPG (UK) | Factor = 4.54609 ÷ 3.785411784

Common conversions

MPG (US)	MPG (UK)

The UK imperial gallon (4.54609 L) is about 20% larger than the US gallon (3.785 L), so UK MPG figures are always higher than US MPG for the same vehicle.

Summary

Enter US MPG to get the UK (imperial) MPG equivalent instantly, with a reverse converter and reference table included.

How it works

Enter a fuel economy value in US MPG in the top input field.
The UK MPG result appears instantly — no button needed.
Use the reverse field to convert UK MPG back to US MPG.
Click "Copy" next to any result to copy it to your clipboard.
Click any row in the reference table to populate the converter.

Use cases

Compare fuel economy specs between American and British car listings.
Convert EPA fuel economy ratings to UK imperial MPG for international buyers.
Verify vehicle efficiency figures when importing a car between the US and UK.
Cross-check manufacturer MPG claims published in different markets.
Convert road-trip fuel consumption estimates between US and UK gallon standards.
Understand why a UK car rated at 50 MPG appears more efficient than a US 40 MPG car.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu