Unit Conversion Calculators

What Is Unit Conversion?

Unit conversion is the process of changing a measurement from one unit to another while preserving the same quantity. Every conversion relies on a conversion factor — a fixed ratio between two units. For example, 1 inch equals exactly 2.54 centimeters, and 1 kilogram equals 2.20462 pounds.

Conversion Types Covered

Our conversion calculators span 10 measurement categories:

• Volume to Weight (Cooking & Baking) — Convert milliliters to grams, cups to grams, tablespoons to grams, and more. These conversions require the density of the ingredient because volume and mass are different physical quantities. 1 mL of water weighs 1 gram, but 1 mL of honey weighs 1.42 grams.
• Weight & Mass — Convert between metric and imperial mass units: kilograms to stones and pounds, milligrams to milliliters (density-dependent), and calories to kilograms (energy-mass equivalence for dietary tracking).
• Volume & Liquid — Convert liters to kilograms, grams to liters, and cubic centimeters to cubic meters. These conversions use substance density for accuracy.
• Length & Area — Convert inches to centimeters (1 in = 2.54 cm), inches to feet, square meters to square feet (1 m² = 10.7639 ft²), and inch-pounds to foot-pounds for torque.
• Temperature — Convert Fahrenheit to Celsius (°F to °C), Celsius to Fahrenheit (°C to °F), Fahrenheit to Kelvin (°F to K), and Celsius to Kelvin (°C to K). The Fahrenheit-Celsius formula is: °C = (°F − 32) × 5/9.
• Time — Convert minutes to hours, seconds to minutes, and days to months. Time conversions use fixed ratios: 60 seconds = 1 minute, 60 minutes = 1 hour.
• Speed & Motion — Convert miles per hour to kilometers per hour (1 mph = 1.60934 km/h) and RPM to radians per second.
• Electrical & Energy — Convert kiloohms to ohms (1 kΩ = 1,000 Ω), megaohms to ohms, megawatt hours to kilowatt hours, million BTU to megawatt hours, and kilocalories to calories.
• Fuel Economy — Convert between miles per gallon (MPG) and liters per 100 kilometers (L/100km), and between kilometers per liter (km/L) and MPG. These are reciprocal conversions used in US and metric automotive standards.
• Angle — Convert degrees to radians (1° = π/180 rad ≈ 0.01745 rad), radians to degrees, degrees to milliradians, and milliradians to degrees. Used in trigonometry, navigation, and ballistics.

How Unit Conversions Work

Most unit conversions follow a straightforward formula: result = input × conversion factor. For example, to convert 12 inches to centimeters: 12 × 2.54 = 30.48 cm. Temperature conversions are different — they use offset formulas because the Fahrenheit, Celsius, and Kelvin scales have different zero points.

Volume-to-weight conversions (like mL to grams) are unique because they require knowing the density of the specific substance. The formula is: mass = volume × density. Our cooking and baking converters include 20 preset ingredient densities — from water (1.0 g/mL) and milk (1.03 g/mL) to flour (0.53 g/mL), sugar (0.85 g/mL), honey (1.42 g/mL), and olive oil (0.92 g/mL).

The Metric System vs. Imperial System

The International System of Units (SI) — commonly called the metric system — is used in most countries worldwide. It is based on seven base units: meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). The United States, Liberia, and Myanmar still primarily use the imperial system (or US customary units) for everyday measurements, using inches, feet, pounds, and Fahrenheit.

This difference is the main reason conversion calculators are essential — whether you're following a European recipe that lists ingredients in grams, reading a scientific paper with SI units, or comparing fuel efficiency between an American car rated in MPG and a European car rated in L/100km.