Unit Converter Guide: Length, Weight, Area, Volume, Temperature
The arithmetic is trivial; the mistakes come from which definition you are using. A US gallon is about 3.785 litres, an imperial gallon about 4.546. An ounce is 28.35 g avoirdupois or 31.10 g troy. Pin down the unit before worrying about precision.
When you need to convert
Following a recipe from abroad, working out floor area for a renovation, comparing volumetric weight for shipping, checking a drive's real capacity, or reading a foreign oven temperature — all routine conversions. The Chinese market units that sit alongside metric ones make it unavoidable: a recipe calling for half a kilo of ribs and a 500 g supermarket label describe the same thing.
The other case is checking a claim. The contract says 100 square metres and the agent says 30 ping; the run was 5 km and the watch says 3.1 miles. Converting confirms both sides mean the same quantity instead of trusting the number that sounds better.
Converting without mistakes
Establish the system first. Gallons come in US (about 3.785 l) and imperial (about 4.546 l), a gap of roughly twenty per cent. Ounces come in avoirdupois (about 28.35 g) and troy (about 31.10 g, for precious metals). The jin is 500 g in mainland China but roughly 600 g in Taiwan and Hong Kong. Same name, different value — that is where most conversion accidents start.
Temperature is a different kind of problem. It is an affine transform, not a scale factor: Fahrenheit = Celsius × 1.8 + 32, so 20°C is 68°F, not 36°F. A difference of 1°C equals a difference of 1.8°F, but 1°C equals 33.8°F — those are not the same statement. In an oven or a fever, ten degrees is the difference between safe and not.
- Length: 1 inch = 2.54 cm exactly; 1 foot = 12 inches = 0.3048 m
- Weight: 1 pound = 453.59237 g exactly; 1 jin = 500 g; 1 liang = 50 g
- Area: 1 mu is about 666.67 m²; 1 hectare = 15 mu
- Data: 1024-based here, the KiB convention, unlike the 1000-based figure on the box
Limits: conversion cannot fix a definition
Data units are the classic ambiguity. Drive vendors sell 1 TB as 1000 GB, or 10 to the 12th bytes, while the operating system displays in powers of 1024, so the same disk shows about 931 GB. Nothing is missing; two different rulers are in use. Network bandwidth is decimal too, so a 1 Gbps link tops out near 125 MB/s.
This tool does not cover currency (rates move hourly and need a timestamp), historical or regional units (the old chi, jin that vary by region), or professional units for lighting and dosage. Floating-point conversion also leaves last-digit noise, so round to the significant figures the job needs instead of copying every decimal into a drawing.
FAQ
Why does a 1 TB drive show only 931 GB?
Vendors label with decimal units, where 1 TB is 10 to the 12th bytes, while the operating system reports in powers of 1024. The ratio comes out near 931. No capacity is missing; the two G's are different G's. A drive sold as 500 GB shows about 465 GB for the same reason.
How do jin, liang and pounds relate?
A mainland Chinese jin is 500 g and a liang is 50 g, so 1 jin is about 1.102 lb. One pound is 453.59237 g, slightly less than a jin. Note that the jin in Taiwan and Hong Kong is about 600 g, and that precious metals use the troy ounce of 31.10 g rather than the 28.35 g avoirdupois ounce.
Why can't temperature be converted by a factor?
Because Celsius and Fahrenheit have different zero points, the relationship is affine: °F = °C × 1.8 + 32. So 0°C is 32°F and 20°C is 68°F, not 20 × 1.8. Only a temperature difference scales by 1.8; an absolute temperature needs the offset as well.
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