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Free measurement and conversion tools
← Back to DashboardAI Learning GymFree measurement and conversion tools
← Back to DashboardHere are some frequently needed conversions at a glance.
| From | To | Multiply by |
|---|---|---|
| Miles | Kilometers | 1.609 |
| Feet | Meters | 0.3048 |
| Inches | Centimeters | 2.54 |
| Yards | Meters | 0.9144 |
| From | To | Multiply by |
|---|---|---|
| Pounds (lbs) | Kilograms (kg) | 0.4536 |
| Kilograms | Pounds | 2.2046 |
| Ounces | Grams | 28.35 |
| Stone | Kilograms | 6.35 |
| From | To | Formula |
|---|---|---|
| Celsius (°C) | Fahrenheit (°F) | (°C × 9/5) + 32 |
| Fahrenheit (°F) | Celsius (°C) | (°F − 32) × 5/9 |
| Celsius (°C) | Kelvin (K) | °C + 273.15 |
Most of the world uses the metric system (meters, kilograms, liters). The United States primarily uses the imperial system (feet, pounds, gallons), though science and medicine in the US use metric. The UK uses a mix — road distances are in miles, but food is often sold in grams. This is why unit converters are so useful for everyday tasks like cooking with foreign recipes, international travel, or online shopping from other countries.
Minor differences come from rounding. This tool uses precise conversion factors and shows up to 6 significant figures. If you need more precision, avoid rounding intermediate results.
Yes — just type a value in either field, or use the swap (⇄) button to flip the from/to units.
In everyday conversation, "weight" usually means mass — how much stuff is in an object. Technically, weight is the force of gravity on a mass, measured in Newtons. For everyday conversions (pounds to kilograms), the distinction doesn't matter.
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The metric system — officially called the International System of Units (SI) — is the world's most widely used measurement system. It is used by every country on Earth for science and medicine, and by most countries for everyday measurements. Understanding how the metric system works makes unit conversion significantly easier because the entire system is based on powers of ten.
The metric system is built on seven fundamental base units from which all other units are derived:
The power of the metric system lies in its consistent prefix system. Each prefix represents a power of ten — converting between metric units is always a matter of moving the decimal point. The same prefixes apply to every base unit — a kilogram is 1,000 grams just as a kilometer is 1,000 meters.
The metric system was developed in France in the 1790s and was designed from the ground up to be logical and consistent. The relationships between units are always powers of ten, making calculations straightforward. The imperial system has irregular relationships — 12 inches in a foot, 3 feet in a yard, 1,760 yards in a mile — that require memorization and make mental arithmetic difficult. By the 20th century, virtually all countries had officially adopted the metric system, with the United States being the most prominent exception for everyday measurements.
The imperial system is the measurement system traditionally used in the United Kingdom and currently used for most everyday purposes in the United States. It evolved over centuries from older English measurement systems and is characterized by irregular conversion factors between units.
Volume units are the most confusing part of the imperial system because US and UK versions of the same unit names represent different amounts:
This distinction matters when following recipes or calculating fuel efficiency across countries.
Temperature is one of the most commonly converted measurements because the three main scales — Celsius, Fahrenheit, and Kelvin — are used in very different contexts around the world.
Used for everyday temperature in most countries. Defined by two fixed points: 0°C is the freezing point of water and 100°C is the boiling point at standard atmospheric pressure. Body temperature is 37°C. A comfortable room is around 20–22°C.
Used for everyday temperature in the United States. Water freezes at 32°F and boils at 212°F. Body temperature is 98.6°F. A comfortable room is around 68–72°F. Conversion formula: °F = (°C x 9/5) + 32, reverse: °C = (°F - 32) x 5/9.
The scientific standard used in physics, chemistry, and engineering. An absolute scale starting at absolute zero — the point where all molecular motion stops. 0K = -273.15°C. No negative Kelvin values exist. Conversion: K = °C + 273.15. Written without a degree symbol.
| Situation | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Water freezes | 0°C | 32°F | 273K |
| Comfortable room | 21°C | 70°F | 294K |
| Human body | 37°C | 98.6°F | 310K |
| Hot summer day | 38°C | 100°F | 311K |
| Water boils | 100°C | 212°F | 373K |
Unit conversion comes up constantly in daily life. Here are the most common real-world situations where knowing how to convert between measurement systems saves time and prevents mistakes.
Recipes from different countries use different measurement systems. A British recipe might call for grams and milliliters while an American recipe uses cups and ounces. Baking is particularly sensitive to measurement errors — a few grams of difference in leavening agents can make the difference between a perfect cake and a flat one. Accurate unit conversion is essential when following recipes from another country.
Travelers from the US visiting most other countries encounter metric units everywhere — road signs in kilometers, temperatures in Celsius, food sold in grams, fuel in liters. The most useful conversions to memorize: 100 km/h is roughly 62 mph, 30°C is hot (86°F), and a liter of water weighs exactly one kilogram.
Body weight is measured in kilograms in most countries and pounds in the United States. When tracking health metrics or using fitness apps that default to different units, conversion is frequently needed. A quick reference: 70 kg is approximately 154 lbs, and 180 cm is approximately 5 feet 11 inches.
Product dimensions for furniture, electronics, and home goods are often listed in the seller's local units — centimeters versus inches for screen sizes, kilograms versus pounds for shipping weights. Checking dimensions before ordering from international retailers prevents receiving items that do not fit.
Science uses metric units universally — all scientific papers and international standards use SI units regardless of the scientist's country. Unit conversion errors in engineering have had serious consequences. The 1999 loss of NASA's Mars Climate Orbiter was directly caused by a unit conversion error — one team used metric units and another used imperial units for a critical navigation parameter, resulting in a $327 million spacecraft being destroyed. This remains one of the most cited examples of why unit consistency matters.