---
title: "Unit Converter — Metric vs Imperial: Length, Weight, Volume by Country"
description: "Convert between metric and imperial units for length, weight, and volume. Learn why the US gallon differs from the UK gallon and which countries use which systems."
url: "https://worldcalculators.org/calculators/unit-converter/"
canonical: "https://worldcalculators.org/calculators/unit-converter/"
---

# Unit Converter

Convert between metric and imperial units for length, weight, and volume. Learn why the US gallon differs from the UK gallon and which countries use which systems.

## Quick answer

To convert, multiply by the unit's factor: 1 inch = 2.54 cm, 1 mile = 1.609 km, 1 pound = 0.4536 kg. The catch is volume — a US gallon (3.785 L) is about 20% smaller than a UK imperial gallon (4.546 L), so the same "gallon" or "pint" differs by country.

## Why the UK Gallon and US Gallon Are Different Sizes

One of the most common unit confusion points: the US and UK both have a unit called the "gallon" but they're not the same size :
This matters enormously for fuel efficiency. If a UK car gets "40 mpg" and a US car gets "40 mpg", the UK car is actually more efficient because it's traveling 40 miles on more fuel (a larger gallon).

## Which Countries Use Metric vs Imperial?

Only three countries have not officially adopted the metric system : the United States, Myanmar (Burma), and Liberia. However, the reality is more nuanced:

## Cooking Measurements: A Common Confusion

Cooking measurements are particularly prone to international confusion. A "cup" is not standardized globally:

Source: https://worldcalculators.org/calculators/unit-converter/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.