Convert measurements, currency, scientific units, data and everyday sizes.
Browse 21 converters plus a related time zone tool. Open a converter to review its factor, units and any regional convention behind the result.
Featured converters
8 toolsStart with everyday length, weight, temperature, volume, area, speed, currency and data conversions.
Scientific and engineering units
4 toolsConvert angles, energy, power and pressure with the correct units.
Digital, data and color
2 toolsWork with number bases and color values.
Clothing and consumer sizes
3 toolsCompare apparel and shoe sizing across regional systems.
Time and specialty conversions
4 toolsHandle fuel economy, cooking temperatures, Roman numerals and clock formats.
Choose and check a converter
Choose the quantity
Pick length for distance, area for surfaces, volume for capacity or the weight tool for units such as pounds and kilograms. Similar names can represent different quantities.
Confirm the standard
Check whether a gallon is US or Imperial, whether digital storage uses decimal or binary units, and which regional clothing chart applies.
Review the result
Look at the factor and rounding shown by the individual tool. Exchange rates and time zone rules can change, so check the date or location used.
Conversions people get wrong most often
| Conversion | Where it goes wrong |
|---|---|
| Gallons | A US gallon is 3.785 litres; an Imperial gallon is 4.546 — about 20% larger. A recipe or fuel figure converted with the wrong one is meaningfully off |
| Data storage | A "gigabyte" means 10⁹ bytes to a drive manufacturer and 2³⁰ to an operating system. That 7% gap is why a 1 TB drive shows as 931 GB — nothing is missing |
| Cups to grams | Depends entirely on the ingredient. A cup of flour is about 120 g; a cup of sugar is 200 g. Any single conversion factor is wrong for most things |
| Temperature | Celsius to Fahrenheit is not a simple multiplication — the scales have different zero points, so the offset must be applied after the ratio |
| Fuel economy | MPG and L/100km move in opposite directions. Higher MPG is better; higher L/100km is worse. They are inversely related, not proportional |
Each converter here handles these distinctions explicitly rather than picking one convention silently — and says which it used.
Frequently asked questions
Quick answers about units, definitions and conversion factors.
Why is my 1 TB drive showing as 931 GB?
Because two definitions of "gigabyte" are in use. Manufacturers use the decimal one — 1 GB = 1,000,000,000 bytes. Windows reports in binary units — 1 GiB = 1,073,741,824 bytes — while still labelling them GB. The drive holds exactly what was advertised; the difference is purely how the number is displayed. The converter shows both.
How many grams in a cup?
There is no single answer, because a cup measures volume and grams measure mass. A cup of flour is roughly 120 g, sugar 200 g, butter 227 g and water 237 g. This is why baking recipes that matter are written by weight — the Cooking Conversion Calculator asks for the ingredient before converting, and any tool that does not is guessing.
Is a US gallon the same as a UK gallon?
No — the Imperial gallon is about 20% larger, at 4.546 litres against 3.785. It affects fuel economy figures noticeably: 40 MPG measured in Imperial gallons is roughly 33 MPG in US gallons, for exactly the same car. Both the Volume Converter and Fuel Economy Converter keep them separate for this reason.
What is gas mark in Celsius?
Gas mark 4 is about 180°C or 350°F — the most common baking temperature. Each mark up adds roughly 14°C. Fan ovens need about 20°C less than the stated conventional temperature, since circulating air transfers heat faster. The Oven Temperature Converter handles all three scales and the fan adjustment.
Do the clothing size converters work for every brand?
They convert between the standard national systems, which is the reliable part. Brand sizing on top of that varies enormously — vanity sizing means a "medium" differs measurably between labels, and Japanese and European fits differ in cut as well as number. Use the conversion as a starting point and the brand's own measurement chart for the final decision.
Do these work offline?
Once the page has loaded, yes — every conversion factor is fixed and runs locally, so losing your connection does not stop them. The one exception is the Currency Converter, which needs live rates and says so.
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