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Unit Converter
The all-in-one converter. Switch between length, weight, temperature, volume, area and speed in one place.
Length
Weight
Temperature
Volume
Area
Speed
All-in-one
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Temperature Converter
Convert instantly between Celsius, Fahrenheit and Kelvin. Essential for cooking, science and travel.
°C
°F
K
°C, °F, K
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Length Converter
Convert between metric and imperial length units. Centimeters, meters, kilometers, inches, feet, yards and miles.
cm
m
km
in
ft
mi
Metric and US
Convert
Weight Converter
Convert between kilograms, pounds, stone, ounces and grams. Covers both metric and imperial weight systems.
kg
lbs
stone
oz
g
Includes stone
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Currency Converter
European Central Bank reference rates for 30 currencies, including USD, EUR, GBP, JPY, CAD and AUD. Updated every business day.
USD
EUR
GBP
JPY
+26
ECB daily rates
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Speed Converter
Convert between kilometers per hour, miles per hour, meters per second, knots and other speed units.
km/h
mph
m/s
knots
Includes knots
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Area Converter
Convert square meters, square feet, acres, hectares and more. Useful for real estate, gardening and land measurement.
m²
ft²
acres
ha
Acres and hectares
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Volume Converter
Convert liters, gallons, cups, fluid ounces, milliliters and other volume units. Perfect for cooking and liquid measurement.
L
gal
cups
fl oz
ml
US and UK units
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Data Storage Converter
Convert between bytes, kilobytes, megabytes, gigabytes, terabytes and petabytes. Essential for developers and IT professionals.
B
KB
MB
GB
TB
SI and binary
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Color Converter
Convert between HEX, RGB, HSL and HSB color formats. Indispensable for designers and frontend developers.
HEX
RGB
HSL
HSB
HEX, RGB, HSL
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Pressure Converter
Convert between pascals, bar, PSI, atmospheres, mmHg and other pressure units. Used in science, engineering and weather.
Pa
bar
PSI
atm
mmHg
PSI and bar
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Calendar Converter
Convert any date between Gregorian, Julian, Islamic (Hijri), Hebrew, Persian, Ethiopian, Coptic, Byzantine, Maya Long Count and more.
Gregorian
Julian
Islamic
Hebrew
Maya
10+ Calendar Systems
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Why Use Our Free Converters?
12 free converters, with every unit conversion built on the exact official factors (NIST), so an inch is exactly 2.54 cm and a pound exactly 0.45359237 kg, not a rounded approximation. US customary and UK imperial units are kept apart where they differ.
Every converter on CalculatorsHub works instantly in your browser, with no forms to submit, no accounts to create and no data stored on our servers. Results update as you type.
Our unit conversion factors are sourced from the International System of Units (SI) and the National Institute of Standards and Technology (NIST). Currency rates are the European Central Bank reference rates, updated every business day. All converters are updated for 2026.
Metric & Imperial
Every measurement converter covers both metric (SI) and US customary units, with UK imperial units where they differ.
Instant & Accurate
Conversion factors are based on official NIST and SI definitions. Results update in real time as you type: no button to press.
Completely Free
All 12+ converters are free forever. No premium tier, no signup, no credit card. Supported by non-intrusive display advertising.
Private by Design
All conversions happen locally in your browser. No input data is ever sent to our servers or stored anywhere.
Exact Factors Worth Knowing
| Conversion | Exact value |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m |
| 1 mile | 1,609.344 m |
| 1 pound | 0.45359237 kg |
| 1 US gallon | 3.785411784 L (231 cubic inches) |
| 1 UK gallon | 4.54609 L |
| 1 acre | 4,046.8564224 m² |
| 1 nautical mile | 1,852 m |
| Celsius to Fahrenheit | °F = °C × 1.8 + 32 |
| Celsius to kelvin | K = °C + 273.15 |
| 1 standard atmosphere | 101,325 Pa |
| 1 KB vs 1 KiB | 1,000 bytes vs 1,024 bytes |
Sources. NIST Special Publication 811 (Guide for the Use of the International System of Units) and NIST Handbook 44, Appendix C; IEC 80000-13 for binary prefixes.
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Converter Questions
Multiply the Celsius value by 9, divide by 5, then add 32. Formula: °F = (°C × 9/5) + 32. Example: 20°C = (20 × 9/5) + 32 = 68°F. To go the other way: °C = (°F − 32) × 5/9. Use our Temperature Converter for instant results without manual calculation.
One pound (lb) equals exactly 0.45359237 kilograms. Conversely, one kilogram equals approximately 2.20462 pounds. To convert pounds to kg, multiply by 0.4536. To convert kg to pounds, multiply by 2.2046. Our Weight Converter handles all weight units including stone (1 stone = 14 lbs = 6.35 kg) and ounces (1 oz = 28.35 g).
One inch equals exactly 2.54 centimeters, by international definition since 1959. So 1 foot (12 inches) = 30.48 cm, and 1 meter = 39.3701 inches. To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54. Our Length Converter covers all common length units including miles, yards, feet, inches, meters and kilometers.
Multiply miles per hour (mph) by 1.60934 to get kilometers per hour (km/h). Example: 60 mph = 96.56 km/h. To convert km/h to mph, multiply by 0.62137. Other common conversions: 1 m/s = 3.6 km/h = 2.237 mph. 1 knot = 1.852 km/h = 1.151 mph. Our Speed Converter handles all of these instantly.
One US gallon equals exactly 3.785411784 liters (about 3.785). Note: the UK (imperial) gallon is larger at 4.54609 liters. Other common volume conversions: 1 liter = 4.22675 US cups = 33.814 fl oz. 1 US cup = 236.588 ml. Our Volume Converter distinguishes between US and UK measurements to avoid confusion.
One acre equals 4,046.86 square meters, or approximately 0.4047 hectares. Conversely, 1 hectare = 2.471 acres = 10,000 m². One square foot = 0.0929 m². These conversions are used frequently in real estate and land measurement. Our Area Converter supports acres, hectares, square meters, square feet, square miles and square kilometers.
In the decimal (SI) system used by hard drive manufacturers: 1 GB = 1,000 MB = 1,000,000 KB = 1,000,000,000 bytes. In the binary system used by Windows: 1 GiB (gibibyte) = 1,024 MiB = 1,048,576 KiB = 1,073,741,824 bytes. This difference explains why a 1 TB hard drive shows as 931 GB in Windows. Our Data Storage Converter handles both, decimal (KB, MB, GB) and binary (KiB, MiB, GiB).
HEX color is a six-digit hexadecimal code (e.g. #FF5733) representing the red, green and blue channels of a color. Each pair of digits (FF, 57, 33) is a hex number from 00 to FF (0 to 255 in decimal). To convert to RGB: R=255, G=87, B=51. To convert RGB to HEX, convert each value to hex and concatenate. Our Color Converter handles HEX, RGB, HSL and HSB automatically.
Once every business day. Our Currency Converter uses the reference rates the European Central Bank publishes at about 16:00 CET, loaded through the free Frankfurter service. These are mid-market style reference rates, not live trading prices, and they do not change during the day. Banks and exchange services add a spread, so confirm the exact rate with them before a transfer.
Mass is the amount of matter in an object, measured in kilograms or pounds-mass. Weight is the gravitational force on that mass, measured in newtons. On Earth's surface they are proportional, so in everyday use (and on our converter) kilograms and pounds are used interchangeably for both. On the Moon you would weigh about one sixth as much but your mass would be unchanged. Our Weight Converter uses the everyday convention.