# Calculate Conversion > Free browser-based unit converters and calculators: length, weight, temperature, volume, speed, area, data storage, pressure, energy, time, fuel economy and currency, plus percentage and profit-margin calculators and a kitchen measures chart. Factors follow the exact international definitions (BIPM, NIST); currency uses European Central Bank reference rates. Each page explains the ambiguous cases (US vs imperial gallons, decimal vs binary GB, three kinds of ton). Nothing a visitor types leaves their browser. ## Converters and calculators - [Length converter](https://calculateconversion.online/length-converter.html): One inch is exactly 2.54 centimetres, by international definition since 1959. From that: 1 foot = 30.48 cm, 1 metre ≈ 3.2808 feet, and 1 mile = 1.609344 km exactly. - [Weight converter](https://calculateconversion.online/weight-converter.html): One pound is exactly 0.45359237 kilograms, so 1 kg ≈ 2.2046 lb. One ounce is about 28.35 g, and one stone is 14 lb, about 6.35 kg. - [Temperature converter](https://calculateconversion.online/temperature-converter.html): To convert Celsius to Fahrenheit, multiply by 9/5 and add 32: °F = (°C × 9/5) + 32. To convert back, subtract 32 and multiply by 5/9. Kelvin is Celsius plus 273.15. - [Volume converter](https://calculateconversion.online/volume-converter.html): A US gallon is 3.785411784 litres and an imperial (UK) gallon is 4.54609 litres, about 20% larger. A US cup is about 236.6 ml, while a metric cup is 250 ml. - [Speed converter](https://calculateconversion.online/speed-converter.html): To convert km/h to mph, divide by 1.609344 (or multiply by about 0.6214). 100 km/h is about 62.1 mph. One metre per second is exactly 3.6 km/h, and one knot is one nautical mile per hour, about 1.852 km/h. - [Area converter](https://calculateconversion.online/area-converter.html): One square metre is about 10.7639 square feet, because area factors are the length factor squared (3.2808² ≈ 10.76). One hectare is 10,000 m², about 2.471 acres, and one acre is 43,560 ft², about 4,046.86 m². - [Data storage converter](https://calculateconversion.online/data-storage-converter.html): In decimal (SI) units, 1 GB is 1,000 MB and 1 TB is 1,000 GB. In binary units, 1 GiB is 1,024 MiB. That is why a 1 TB drive (10¹² bytes) shows as about 931 GB in Windows, which counts in binary units but labels them GB. - [Pressure converter](https://calculateconversion.online/pressure-converter.html): One bar is about 14.504 psi, and one standard atmosphere is 101,325 Pa, which is 1,013.25 hPa or 14.696 psi. A bar (100,000 Pa) is about 1.3% smaller than an atmosphere. - [Energy converter](https://calculateconversion.online/energy-converter.html): One food Calorie (kilocalorie, kcal) is exactly 4.184 kilojoules. One kilowatt-hour is exactly 3,600,000 joules. A small calorie (cal) is a thousand times smaller than a food Calorie. - [Time converter](https://calculateconversion.online/time-converter.html): There are exactly 60 seconds in a minute, 3,600 in an hour, 86,400 in a day and 604,800 in a week. Months and years are averages: an average month is about 4.35 weeks, and a 365-day year is 8,760 hours. - [Fuel economy converter](https://calculateconversion.online/fuel-economy-converter.html): To convert US mpg to litres per 100 km, divide 235.215 by the mpg figure. For imperial (UK) mpg, divide 282.481 by the mpg. The same division converts back, because the two measures are reciprocals. - [Currency converter](https://calculateconversion.online/currency-converter.html): This converter uses the European Central Bank's daily euro foreign-exchange reference rates, shown with their date. They are mid-market reference rates, so the rate a bank, card or exchange counter gives you will usually be less favourable. - [Profit margin calculator](https://calculateconversion.online/profit-margin-calculator.html): Profit margin is profit divided by revenue, times 100. Profit is revenue minus item costs minus selling fees. Markup is profit divided by cost, so the same sale has a higher markup than margin. - [Percentage calculator](https://calculateconversion.online/percentage-calculator.html): To find X% of Y, multiply Y by X ÷ 100. To find what percent A is of B, divide A by B and multiply by 100. Percentage change is (new − old) ÷ old × 100. - [Kitchen conversion chart](https://calculateconversion.online/kitchen-volume-conversion-chart.html): A US customary cup is about 236.6 ml, while a metric (and Australian) cup is 250 ml. A US or metric tablespoon is about 15 ml, but an Australian tablespoon is 20 ml. A teaspoon is 5 ml almost everywhere. - [180 cm in feet and inches](https://calculateconversion.online/180-cm-in-feet.html): 180 cm = 5.9055 feet = 5 feet 10.87 inches; about 5 ft 11 in to the nearest inch. ## About - [About and sources](https://calculateconversion.online/about.html): exact definitions used, where units are ambiguous, accuracy limits, corrections, funding - [Contact](https://calculateconversion.online/contact.html): report a wrong factor or request a converter ## Optional - [Full text of every page](https://calculateconversion.online/llms-full.txt) - [Privacy and cookie policy](https://calculateconversion.online/privacy.html)