Convert between units of length, weight, volume, temperature, area, speed, and more.
Unit conversion calculators translate measurements between metric, US customary, and imperial systems instantly and accurately. Whether you are converting a recipe from grams to ounces, calculating road distances in miles and kilometers, reading a product specification in unfamiliar units, or working across metric and imperial standards in a professional context, these tools use internationally accepted conversion factors and are accurate to at least six significant figures.
All-in-one unit conversion tool for any measurement category.
Open calculator →Convert any length or distance unit instantly with formulas and examples.
Open calculator →Convert weight and mass units in any direction, with common conversion tables.
Open calculator →Convert °F, °C, and Kelvin instantly with formulas and reference points.
Open calculator →Convert liquid and dry volume units instantly with a full quick-reference table.
Open calculator →All common unit types in one place: Unit Converter. Length or distance specifically (inches, feet, meters, miles, km): Length Converter. Weight or mass (pounds, kilograms, ounces, grams): Weight Converter. Temperature (Fahrenheit, Celsius, Kelvin): Temperature Converter. Liquid or dry volume (cups, liters, gallons, ml): Volume Converter. For a focused single-pair conversion with a formula explanation, common values table, and examples: use the dedicated conversion pages — Inches to CM, CM to Inches, KG to LBS, LBS to KG, Fahrenheit to Celsius, Celsius to Fahrenheit, Cups to ML, and ML to Cups.
The metric system (officially called the International System of Units, or SI) is used by nearly every country in the world for science, medicine, trade, and everyday measurements. The United States is one of only three countries — alongside Myanmar and Liberia — that still primarily uses customary units for everyday purposes like road distances, body weight, and cooking. In science and medicine, even the US uses metric exclusively. The metric system's base-10 structure makes arithmetic straightforward; US customary units have irregular ratios (12 inches per foot, 3 feet per yard, 5,280 feet per mile, 16 ounces per pound) that require conversion tools more often. Understanding both systems is increasingly important as recipes, products, specifications, and workplaces cross borders.
Length: 1 inch = 2.54 cm (exact). 1 foot = 30.48 cm. 1 yard = 0.9144 m. 1 mile = 1,609.34 m = 1.609 km. 1 km = 0.6214 miles. Weight: 1 pound = 453.592 grams. 1 ounce = 28.35 grams. 1 kilogram = 2.2046 pounds. 1 short ton (US) = 907.2 kg. 1 metric ton = 1,000 kg. Volume: 1 US cup = 236.6 ml. 1 US gallon = 3.785 liters. 1 fluid ounce = 29.57 ml. Temperature: °C = (°F − 32) × 5/9. °F = °C × 9/5 + 32. 0°C = 32°F. 100°C = 212°F. 37°C = 98.6°F.
For most everyday uses — cooking, DIY projects, travel distances, personal weight — rounding to two or three decimal places is more than sufficient. For engineering, scientific, or medical calculations, use the full conversion factor and pay attention to significant figures. Note that some conversions are exact by definition (1 inch = exactly 2.54 cm; 1 pound = exactly 453.59237 grams) while others are rounded approximations. When converting between units that involve temperature scales, remember that temperature conversions use an offset formula (not just multiplication), so they cannot be combined by simple ratio scaling.
Cooking and baking: metric recipes from UK, European, or Australian sources need volume and weight conversions to US units. Running and cycling: race distances alternate between miles and kilometers internationally — 5K = 3.1 miles, 10K = 6.2 miles, marathon = 26.2 miles = 42.2 km. Construction and home improvement: lumber, hardware, and tools are labeled in different systems by country of manufacture. International shopping: clothing and shoe sizes, screen sizes, and product dimensions often use the system of the country of origin. Science and engineering: virtually all international standards and technical specifications use SI units.