Unit Converter Guide: Convert Units Accurately

Unit conversion is the process of converting a measurement from one unit to another. For example, converting miles to kilometers or pounds to kilograms. This is essential for creating a common understanding across different measurement systems, and our Unit Converter makes this instant.

The basic formula for unit conversion is:

Example:

Convert 5 kilometers to miles:

Metric System (SI Units)

Used by most countries worldwide. Based on powers of 10, making conversions simple. Standard units include:

• Length: Meter (m)
• Mass: Kilogram (kg)
• Volume: Liter (L)
• Temperature: Celsius (°C)

U.S. Customary and British Imperial Units

U.S. customary and British Imperial measurement systems share several unit names, but they are not identical. This matters most for volume: a U.S. liquid gallon and an Imperial gallon have different sizes. The converter therefore names U.S. volume units explicitly and labels the Imperial gallon separately.

• Shared length names: inch, foot, yard, and mile
• Supported U.S. mass units: ounce, pound, and U.S. ton
• Supported U.S. volume units: teaspoon, tablespoon, fluid ounce, legal cup, liquid pint, liquid quart, and liquid gallon
• Supported Imperial volume unit: gallon
• Supported temperature scale: Fahrenheit (°F)

Length Conversions

• 1 inch = 2.54 centimeters
• 1 foot = 12 inches = 0.3048 meters
• 1 yard = 3 feet = 0.9144 meters
• 1 mile = 1.60934 kilometers
• 1 meter = 39.37 inches
• 1 kilometer = 0.621371 miles

Weight/Mass Conversions

• 1 ounce = 28.35 grams
• 1 pound = 453.592 grams = 0.453592 kilograms
• 1 kilogram = 2.20462 pounds
• 1 metric ton = 1000 kilograms = 2204.62 pounds
• 1 stone = 14 pounds = 6.35029 kilograms

Volume Conversions

• 1 fluid ounce (US) = 29.5735 milliliters
• 1 U.S. legal cup = 240 milliliters
• 1 U.S. liquid pint = 473.176473 milliliters
• 1 U.S. liquid quart = 946.352946 milliliters
• 1 U.S. liquid gallon = 3.785411784 liters
• 1 Imperial gallon = 4.54609 liters

Select the unit whose label matches the source. Do not substitute an Imperial gallon for a U.S. liquid gallon or assume that an unlabelled recipe cup equals the calculator's 240 mL U.S. legal cup.

Temperature Conversions

Celsius to Fahrenheit

Convert 25°C to Fahrenheit:

Fahrenheit to Celsius

Convert 98.6°F to Celsius:

Metric units use prefixes for easy scaling:

International Trade

Different countries use different unit systems. Accurate conversions are essential for trade, shipping, and commerce.

Science and Engineering

Scientific research often requires unit conversions. Scientists globally use metric units for consistency.

Cooking and Recipes

Recipes use different volume conventions. This tool can convert supported volume units such as a U.S. legal cup to milliliters. It cannot directly convert cups to grams because that requires the ingredient's density, and an unlabelled recipe cup may follow a different convention.

Medicine and Healthcare

Medication instructions can depend on concentration, dose, patient factors, and approved measuring devices. Do not use this general-purpose converter as a substitute for prescription directions, a pharmacist, or a clinical calculation system.

Rounding Errors

Rounding a conversion factor or intermediate value too early can introduce error. Use an appropriate published factor and round the final result to the precision your source measurement supports.

Reversing Conversions

Accidentally converting in the wrong direction. Always check whether you're multiplying or dividing.

Mixing Unit Systems

Using units from different systems in calculations without converting first. Always standardize units first.

Ignoring Significant Figures

Not considering precision. Express results with the same precision as the input data.

• Remember 1 km ≈ 0.6 miles (handy for road signs)
• Remember 1 liter ≈ 0.264 U.S. liquid gallons or 0.220 Imperial gallons
• Remember 1 pound ≈ 0.45 kg (helpful for weight conversions)
• For a rough everyday temperature estimate: °F ≈ (°C × 2) + 30

Unit conversion is useful in science, engineering, cooking, and international communication. The important first step is choosing the correct source unit, especially when a U.S. and Imperial volume unit share a name.

Use our Unit Converter for supported metric, U.S. customary, Imperial gallon, or temperature conversions, and preserve enough precision for your use case.