Imperial Converter

Convert between imperial and metric units instantly. Accurate conversions for length, weight, volume, temperature, and more.

Length
Weight
Volume
Temperature
Area
Speed
Quick Conversions
Conversion Results
10 feet = 3.048 meters
Common Equivalents
Conversion History

Imperial vs Metric Systems

The Imperial system (used primarily in the United States) and the Metric system (used in most other countries) are two different systems of measurement. This converter helps you easily switch between them.

Imperial / US Customary System

The Imperial system originated in Britain and is now primarily used in the United States (as US customary units). Key characteristics:

  • Based on historical precedents and human-scale measurements
  • Uses feet, pounds, gallons, Fahrenheit
  • Not decimal-based (12 inches in a foot, 3 feet in a yard)
  • Still used in the US, Liberia, and Myanmar
Metric System (SI)

The International System of Units (SI) is the modern form of the metric system. Key characteristics:

  • Decimal-based system (powers of 10)
  • Used worldwide in science, medicine, and most countries
  • Uses meters, kilograms, liters, Celsius
  • Designed for simplicity and consistency

Conversion Tables

Length Conversions
Imperial / US Metric Equivalent Common Usage
1 inch 2.54 centimeters Small measurements, screen sizes
1 foot (12 inches) 0.3048 meters Height, room dimensions
1 yard (3 feet) 0.9144 meters Fabric, football field
1 mile (5280 feet) 1.609 kilometers Road distances
1 nautical mile 1.852 kilometers Marine and air navigation
Weight / Mass Conversions
Imperial / US Metric Equivalent Common Usage
1 ounce (oz) 28.35 grams Small items, food portions
1 pound (16 oz) 0.4536 kilograms Body weight, produce
1 stone (14 lbs) 6.35 kilograms Body weight (UK)
1 US ton (2000 lbs) 0.9072 tonnes Vehicle weight, shipping
1 UK ton (2240 lbs) 1.016 tonnes Shipping (UK)
Volume Conversions
Imperial / US Metric Equivalent Common Usage
1 teaspoon (tsp) 4.929 milliliters Cooking, medicine
1 tablespoon (tbsp) 14.79 milliliters Cooking
1 fluid ounce (fl oz) 29.57 milliliters Beverages, cooking
1 US cup (8 fl oz) 236.6 milliliters Cooking
1 US pint (16 fl oz) 473.2 milliliters Beverages
1 US quart (32 fl oz) 0.9464 liters Liquids, motor oil
1 US gallon (128 fl oz) 3.785 liters Fuel, milk
1 UK gallon 4.546 liters Fuel, milk (UK)

Temperature Conversion Formulas:

  • Fahrenheit to Celsius: °C = (°F - 32) × 5/9
  • Celsius to Fahrenheit: °F = (°C × 9/5) + 32
  • Celsius to Kelvin: K = °C + 273.15
  • Kelvin to Celsius: °C = K - 273.15

Quick Reference Guide

Common Length Conversions
  • 1 inch = 2.54 cm
  • 1 foot = 30.48 cm
  • 1 yard = 0.914 m
  • 1 mile = 1.609 km
  • 1 cm = 0.3937 inches
  • 1 m = 3.281 feet
  • 1 km = 0.6214 miles
Common Weight Conversions
  • 1 oz = 28.35 g
  • 1 lb = 0.4536 kg
  • 1 stone = 6.35 kg
  • 1 US ton = 907.2 kg
  • 1 g = 0.03527 oz
  • 1 kg = 2.205 lbs
  • 1 tonne = 1.102 US tons
Common Volume Conversions
  • 1 tsp = 4.929 mL
  • 1 tbsp = 14.79 mL
  • 1 fl oz = 29.57 mL
  • 1 cup = 236.6 mL
  • 1 pint = 473.2 mL
  • 1 quart = 0.9464 L
  • 1 gallon = 3.785 L

Frequently Asked Questions

Imperial units were standardized in the British Empire in 1824. US customary units evolved from English units used in the American colonies before independence. They are very similar but have some differences, particularly in volume measurements (e.g., US gallon vs Imperial gallon).

The US continues to use imperial units primarily due to tradition, infrastructure costs, and cultural familiarity. Transitioning to the metric system would require significant changes to manufacturing, education, and public infrastructure. However, the metric system is officially recognized and used in science, medicine, and many industries.

No, fluid ounces measure volume, while ounces (avoirdupois) measure weight. A fluid ounce of water weighs approximately 1.043 ounces at room temperature, but this varies for different substances due to density differences.

Conversions are accurate to at least 6 significant figures, which is sufficient for most practical applications. For scientific or engineering purposes requiring extreme precision, you should consult official standards from organizations like NIST (National Institute of Standards and Technology).

Useful estimation tricks:
  • Miles to km: multiply by 1.6 (or add half then 10%)
  • Feet to meters: divide by 3
  • Pounds to kg: divide by 2 then subtract 10%
  • Fahrenheit to Celsius: subtract 30 then halve (rough estimate)
  • Gallons to liters: multiply by 4