Unit Converter: Instantly Convert Length, Weight, Temperature & More (Free Online Tool)
Whether you're cooking a recipe from an American cookbook, calculating fuel efficiency on a road trip, or working on a school science project, unit conversion is something everyone needs — and gets wrong. Our free online unit converter makes it effortless. No formulas. No math. Just instant, accurate results.
This guide covers everything you need to know: the most common unit conversions, how they work, and the quickest ways to convert between metric and imperial measurements.
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Convert length, weight, temperature, speed, area, volume and more — instantly.
Open Unit Converter →What Is a Unit Converter?
A unit converter is a tool that transforms a measurement from one unit to another without changing its physical quantity. For example, 1 kilometer and 0.621 miles refer to the exact same distance — only the label changes.
Unit converters are used by students, engineers, chefs, travelers, scientists, and everyday people around the world. The two dominant measurement systems are:
- Metric System (SI) — Used by most of the world. Based on powers of 10. Includes meters, kilograms, liters, and Celsius.
- Imperial System (US Customary) — Used primarily in the United States. Includes feet, pounds, gallons, and Fahrenheit.
Length & Distance Conversions
Length is the most commonly converted unit. Whether you're measuring a room, planning a run, or reading a map, these conversions come up constantly.
Key Length Conversion Facts
| From | To | Multiply By |
|---|---|---|
| Kilometers (km) | Miles (mi) | × 0.621371 |
| Miles (mi) | Kilometers (km) | × 1.60934 |
| Meters (m) | Feet (ft) | × 3.28084 |
| Feet (ft) | Meters (m) | × 0.3048 |
| Centimeters (cm) | Inches (in) | × 0.393701 |
| Inches (in) | Centimeters (cm) | × 2.54 |
Weight & Mass Conversions
Weight conversion is essential in cooking, fitness, shipping, and science. The metric system uses grams and kilograms, while the imperial system uses ounces and pounds.
| From | To | Multiply By |
|---|---|---|
| Kilograms (kg) | Pounds (lb) | × 2.20462 |
| Pounds (lb) | Kilograms (kg) | × 0.453592 |
| Grams (g) | Ounces (oz) | × 0.035274 |
| Ounces (oz) | Grams (g) | × 28.3495 |
| Metric Ton (t) | Pounds (lb) | × 2204.62 |
| Stone (st) | Kilograms (kg) | × 6.35029 |
Temperature Conversions
Temperature conversion is unique because it uses formulas rather than simple multiplication. The three major scales are Celsius (°C), Fahrenheit (°F), and Kelvin (K).
Temperature Conversion Formulas
| 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 |
| Kelvin (K) | Celsius (°C) | K − 273.15 |
Common Temperature Reference Points
| Situation | Celsius | Fahrenheit |
|---|---|---|
| Water freezes | 0 °C | 32 °F |
| Room temperature | 20–22 °C | 68–72 °F |
| Human body temperature | 37 °C | 98.6 °F |
| Water boils | 100 °C | 212 °F |
| Oven (moderate heat) | 175 °C | 350 °F |
Speed Conversions
Speed conversions matter for driving, sports, aviation, and weather. The most common conversion is between kilometers per hour (km/h) and miles per hour (mph).
| From | To | Multiply By |
|---|---|---|
| km/h | mph | × 0.621371 |
| mph | km/h | × 1.60934 |
| Meters/second (m/s) | km/h | × 3.6 |
| Knots (kn) | km/h | × 1.852 |
| Knots (kn) | mph | × 1.15078 |
Area Conversions
Area conversions are critical in real estate, agriculture, engineering, and interior design. Note that area units are squared, which changes the conversion factors significantly.
| From | To | Multiply By |
|---|---|---|
| Square meters (m²) | Square feet (ft²) | × 10.7639 |
| Square feet (ft²) | Square meters (m²) | × 0.092903 |
| Hectares (ha) | Acres | × 2.47105 |
| Acres | Hectares (ha) | × 0.404686 |
| Square kilometers (km²) | Square miles (mi²) | × 0.386102 |
Volume & Liquid Conversions
Volume conversions are especially common in cooking and chemistry. The US and UK both have "gallons" but they are different sizes — always check which one you mean!
| From | To | Multiply By |
|---|---|---|
| Liters (L) | US Gallons | × 0.264172 |
| US Gallons | Liters (L) | × 3.78541 |
| Milliliters (mL) | US Fluid oz | × 0.033814 |
| US Cups | Milliliters (mL) | × 236.588 |
| Tablespoons (tbsp) | Milliliters (mL) | × 14.7868 |
| Teaspoons (tsp) | Milliliters (mL) | × 4.92892 |
Why Use an Online Unit Converter?
Manual calculations are error-prone — especially with multi-step temperature formulas or when you're mid-recipe and can't afford a mistake. An online unit converter gives you:
- Instant results — no formula memorization required
- High accuracy — precise to multiple decimal places
- All categories in one place — length, weight, temperature, speed, area, volume, and more
- Mobile-friendly — works perfectly on any phone or tablet
- No signup needed — completely free, open to everyone
Convert Any Unit in Seconds
From kilometers to miles, kilograms to pounds, Celsius to Fahrenheit — all free.
Use the Free Converter →Frequently Asked Questions
These are the most common unit conversion questions people search for online.
How do I convert kilometers to miles?
How do I convert Celsius to Fahrenheit?
How many grams are in a pound?
What is the difference between metric and imperial units?
How do I convert square feet to square meters?
How many teaspoons are in a tablespoon?
Is this unit converter free to use?
Start Converting Now
You now have a solid grasp of the most important unit conversions in everyday life. Whether it's for a recipe, a road trip, a science project, or understanding a foreign product listing, our unit converter is here to help — instantly and accurately.
Bookmark our free unit converter and never get stuck on a conversion again. It's fast, it's free, and it covers every unit you'll ever need.