Unit Converter
Converting Units Across Five Everyday Categories
Units of measurement create a shared language for describing the physical world — but the language isn't universal. The metric and imperial systems co-exist across science, engineering, cooking, construction, and everyday life. Being fluent in both means never being stuck in a recipe, a technical spec, or a travel situation because the numbers are in unfamiliar units.
How to Use This Calculator
Select a category (Length, Weight, Temperature, Volume, or Speed), enter a value, and select the source unit. Hit Convert to see the value in every unit within that category simultaneously. For more units in a specific category, use the dedicated converters linked in the sidebar.
How Unit Conversion Works
For length, everything converts through meters (1 meter = base). 1 foot = 0.3048 m. 1 inch = 0.0254 m. To convert 6 feet to centimeters: 6 × 0.3048 m = 1.8288 m = 182.88 cm. Temperature is the exception — it uses offset formulas, not simple multiplication.
Temperature Conversion Formulas
Key references: water freezes at 0°C / 32°F / 273.15K; water boils at 100°C / 212°F; body temperature = 37°C / 98.6°F; room temperature = 20–22°C / 68–72°F; absolute zero = 0 K / −273.15°C.
Quick Reference: Most Common Conversions
- Length: 1 inch = 2.54 cm | 1 foot = 0.3048 m | 1 mile = 1.609 km
- Weight: 1 pound = 453.6 g | 1 kg = 2.205 lbs | 1 ounce = 28.35 g
- Volume: 1 US gallon = 3.785 L | 1 cup = 236.6 mL | 1 fl oz = 29.57 mL
- Speed: 1 mph = 1.609 km/h | 1 knot = 1.852 km/h | 1 m/s = 3.6 km/h
Frequently Asked Questions
What's the difference between mass and weight?
Mass is the amount of matter in an object — constant everywhere in the universe. Weight is the force of gravity on that mass — it varies by location (you weigh slightly less on a mountain than at sea level, and much less on the moon). In everyday life, both terms are used interchangeably. Kilograms and pounds both measure mass in practice, though technically pounds is a force unit. The distinction matters significantly in physics and engineering.
Is a US cup the same as a metric cup?
No — a US cup = 236.6 mL. A metric cup (Australia, Canada) = 250 mL. A US legal cup (FDA nutrition labeling) = 240 mL. For most cooking, the difference is insignificant. For precise baking, use weight (grams) instead of volume — a cup of flour can weigh anywhere from 120–160g depending on how it's packed, while 120g is always 120g.
What is a nautical mile and why is it still used?
One nautical mile = 1.852 km ≈ 1 minute of latitude arc on Earth's surface. This makes navigation elegant: traveling 60 nautical miles north moves you exactly 1° of latitude. No conversion needed. Aviation and maritime navigation use nautical miles and knots worldwide for this reason, deeply embedded in international standards and air traffic control.
How do I convert between US and UK fluid measures?
They differ: 1 US fl oz = 29.57 mL; 1 UK fl oz = 28.41 mL. A US gallon = 3.785 L; a UK gallon = 4.546 L (about 20% more). A US pint = 473 mL; a UK pint = 568 mL. The UK pint is larger — which is why "a pint" at a US bar is noticeably smaller than at a UK pub. When following UK recipes in the US, always specify the country of origin when using the converter.
What is Kelvin used for?
Kelvin is the SI base unit of temperature used in science and physics. Unlike Celsius and Fahrenheit, Kelvin has no negatives because 0 K is absolute zero — where molecular motion theoretically stops. Kelvin is used in thermodynamics, chemistry, and astrophysics, and appears in light bulb color temperature ratings: 2700 K = warm white, 4000 K = neutral white, 5000–6500 K = cool daylight.