Free unit converters for length, weight, area, temperature, speed, and number bases. Includes India-specific land units and instant bidirectional conversion.
Every calculator on iCalcApp is free with no sign-up, and no data collection. Calculations run instantly in your browser — your inputs are never sent to our servers.
All formulas are reviewed by Mayra, and cross-verified against official sources (RBI, WHO, ICMR, ISO).
iCalcApp unit converters cover temperature, length, weight, area, speed, and hexadecimal. All use exact SI-defined conversion factors from BIPM. Includes Indian land units (bigha, gunta, cent), imperial and metric, and real-world reference tables. Free and instant.
Historical measurement systems developed independently before standardisation. The metric system was formalised in France (1795) and is now official in 195 countries. The US, Myanmar, and Liberia have not formally adopted metric for everyday use. The UK uses a hybrid — metric for most official purposes, imperial for road distances and some food portions. This is why international recipes, engineering specs, and product labelling often require conversion.
The International System of Units (SI) is the modern metric system, maintained by the BIPM. It defines 7 base units — metre, kilogram, second, ampere, kelvin, mole, candela — from which all other units derive. SI is the global standard for science, medicine, and international trade. All iCalcApp converters use SI-defined exact factors, not approximations.
Quick unit conversions, all on one pattern: the area converter, hex converter, length converter, speed converter, temperature converter, unit converter, and the weight converter. Each opens instantly, calculates in real time as you type, and explains its formula with worked examples below the tool.
The most-searched conversions globally: km to miles (×0.621), kg to pounds (×2.205), Celsius to Fahrenheit (×9/5 +32), metres to feet (×3.281), and litres to gallons (×0.264 US / ×0.220 UK). For India: square feet to square metres (÷10.764), and land units (1 bigha = 27,225 sq ft in Punjab; 1 cent = 435.6 sq ft in South India).
Indian land units vary by state. Use the Area Converter which includes: Bigha (Punjab: 27,225 sq ft; UP/Bihar: 27,000 sq ft; West Bengal: 14,400 sq ft), Gunta/Guntha (1,089 sq ft in Maharashtra/Karnataka), Cent (435.6 sq ft in South India), and Ground (2,400 sq ft in Tamil Nadu). Always verify with local revenue records.
1 US gallon = 3.785 litres. 1 UK imperial gallon = 4.546 litres — about 20% larger. When converting litres to gallons, always specify which: 10 litres = 2.64 US gallons or 2.20 UK gallons. Fuel economy (MPG) figures also differ — UK MPG is always higher than US MPG for the same vehicle.
iCalcApp converters use the exact conversion factors defined by the International System of Units (SI) and the BIPM (Bureau International des Poids et Mesures). For example, 1 inch = 2.54 cm exactly (defined). 1 mile = 1,609.344 metres exactly. Rounded factors (e.g. 1 kg ≈ 2.2 lbs) introduce small errors — use the converter for full precision.
Yes — all converters support both metric (SI) and imperial/US customary units. The Unit Converter handles the most common cross-system conversions. The Temperature Converter includes Celsius (metric), Fahrenheit (US/imperial), and Kelvin (scientific). The Length Converter covers metres through to miles and nautical miles.
Sources: BIPM — The International System of Units (SI), 9th edition, 2019; NIST Special Publication 811; Revenue Department of India land measurement standards.
For mathematical calculations beyond conversion, see our math calculators.
The length converter handles all units: kilometres, miles, metres, centimetres, millimetres, feet, inches, yards, and nautical miles — with instant bidirectional conversion. Common needs: km to miles for international speed limits, cm to feet for height, metres to feet for property dimensions.
The weight converter covers kilograms, pounds, stone, ounces, grams, tonnes, and traditional Indian units (tola, ser, maund). Gold is quoted per tola in India (1 tola = 11.664 g). Body weight comparisons between India (kg) and US/UK (pounds) are among the most common uses.
The area converter converts between square metres, square feet, acres, hectares, and Indian land units including bigha, gunta, cent, marla, and ground — covering all major regional variations by state. Essential for property purchases, agricultural land transactions, and flooring calculations.
The temperature converter converts between Celsius, Fahrenheit, Kelvin, and Rankine. Quick references: 0°C = 32°F (freezing); 37°C = 98.6°F (body temperature); 100°C = 212°F (boiling at sea level). Kelvin is used in physics and chemistry (0 K = −273.15°C absolute zero).
The speed converter handles km/h, mph, m/s, knots, Mach, and feet per second. India uses km/h for speed limits; the US and UK use mph. Aviation uses knots. Beaufort scale wind speeds are also included.
The hex converter converts between decimal, hexadecimal, binary, and octal — with HTML colour code lookup. Essential for web development, network administration, and embedded systems programming.
The unit converter covers all categories in one place — length, weight, volume, area, temperature, and more. Use it when you need a quick conversion across multiple unit types without switching between specialist converters.
| From | To | Multiply By |
|---|---|---|
| Miles | Kilometres | 1.609344 |
| Kg | Pounds | 2.204623 |
| Celsius | Fahrenheit | ×1.8, then +32 |
| Square feet | Square metres | 0.092903 |
| Acres | Hectares | 0.404686 |
| Litres | Gallons (US) | 0.264172 |
| Unit | Common use cases | India-specific need |
|---|---|---|
| Length | km to miles, feet to cm, height conversions | Feet/inches ↔ cm for height; km ↔ miles for international travel |
| Weight | kg to lbs, body weight, gold in tola | 1 tola = 11.664 g; gold prices quoted per 10g or per tola in India |
| Area | sq ft to sq m, bigha, acres, hectares | Property in sq ft (RERA), land in bigha/gunta/cent by state |
| Temperature | °C ↔ °F ↔ Kelvin | Medical readings in °F, weather in °C, chemistry in Kelvin |
| Speed | km/h ↔ mph, m/s, knots | Indian speed limits in km/h; international driving and aviation in mph/knots |
| Hex / Binary | Decimal ↔ hex ↔ binary ↔ octal | Web colours (#RRGGBB), IP addressing, embedded systems |
| General | Any category, quick one-off conversions | Hub for all conversion types without switching between pages |
All conversion factors on iCalcApp use internationally standardised values. Length uses the international yard and pound agreement (1959). Temperature uses the exact thermodynamic definitions (0°C = 273.15 K). Area uses SI base units (1 m² = 10.7639 sq ft, exact). Indian land units (bigha, gunta, cent) vary by state — our area converter uses the most widely accepted national averages with state-specific notes.
For precision engineering or legal/official conversions, verify against BIPM (International Bureau of Weights and Measures) or the relevant national standards body (BIS in India). View our methodology.