The Xunits Unit Wiki is designed to complement the converter pages. A converter answers a calculation. A unit guide explains what the unit is, where it belongs, how it relates to neighboring units, and which mistakes matter in real measurement work.
What is a unit of measurement?
A unit of measurement is a defined quantity used as a reference for comparing physical, mathematical, or technical values. A length such as 12 cm, a mass such as 5 kg, a temperature such as 20 C, and a data rate such as 100 Mbps all combine a number with a unit. The number describes magnitude; the unit describes what kind of quantity is being measured.
Major unit systems
Metric and SI units
Metric units use decimal prefixes such as milli-, centi-, kilo-, and mega-. The International System of Units provides the modern standard base units and coherent derived units used in science, engineering, trade, and education.
Imperial and US customary units
Imperial and US customary units include inches, feet, yards, miles, pounds, fluid ounces, gallons, and related units. They remain common in US consumer products, construction, travel, and everyday communication.
How unit symbols and prefixes work
Unit symbols are compact labels such as cm, kg, L, W, Pa, and MB. They are not ordinary abbreviations, so they usually do not take a plural s. Prefixes change the magnitude of a unit: kilo- means one thousand, centi- means one hundredth, and milli- means one thousandth.
| Prefix | Meaning | Example | Relationship |
|---|---|---|---|
| milli- | one thousandth | millimeter | 1 mm = 0.001 m |
| centi- | one hundredth | centimeter | 1 cm = 0.01 m |
| kilo- | one thousand | kilometer | 1 km = 1,000 m |
| mega- | one million | megabyte | 1 MB = 1,000,000 bytes in decimal storage |
How to use this wiki
Different readers need different levels of unit detail. Xunits unit guides are organized so a quick reader can get the definition immediately, while a technical reader can continue into formulas, exact relationships, usage notes, and common mistakes.
Everyday users
Start with the quick facts, visual scale, and common examples. This is useful for shopping, recipes, travel, product dimensions, and quick measurement checks.
Students and teachers
Use the definition, prefix tables, hierarchy diagrams, and FAQ sections to connect unit meaning with classroom measurement and conversion practice.
Technical readers
Check exact relationships, rounding notes, symbol conventions, and standards-style reference notes before using values in specifications or calculations.
Browse by measurement category
The wiki will grow by measurement category so related units stay close together. Some categories already have hand-written guides, while others currently link to converter hubs until their unit guides are written.
Length
Distance, size, height, width, depth, and scale. Current guides: meter, centimeter, millimeter, inch, foot, yard, kilometer, and mile.
Weight and mass
Kilograms, pounds, grams, ounces, and related mass units. Browse the Weight and Mass Unit Wiki.
Temperature
Celsius, Fahrenheit, Kelvin, temperature scales, offsets, and formula differences. Current guide: Celsius. Browse the Temperature Unit Wiki.
Pressure
Pascals, kilopascals, bar, psi, atmospheres, and torr. Browse the Pressure Unit Wiki.
Data storage
Bytes, decimal storage, and binary storage. Browse the Data Storage Unit Wiki.
Data transfer rate
Bits per second, bytes per second, Mbps, MB/s, and throughput units. Browse the Data Transfer Rate Unit Wiki.
Power
Watts, kilowatts, megawatts, horsepower, and BTU per hour. Browse the Power Unit Wiki.
Common unit mistakes
Many measurement errors happen because the number is correct but the unit is misunderstood. The wiki pages call out these boundaries directly so readers can avoid silent mistakes.
- Mixing unit symbols with unit names, such as writing "cms" instead of "cm".
- Confusing linear, square, and cubic units, such as cm, cm2, and cm3.
- Rounding too early when converting between metric and customary units.
- Comparing decimal and binary data units without checking how the source defines them.
- Using a familiar everyday unit inside a technical formula that expects SI base units.
Editorial standard
Each Xunits guide is written as a standalone reference article. The goal is not to repeat a dictionary definition, but to explain the unit from every practical angle: definition, symbol, exact relationships, visual scale, common contexts, mistakes, formulas, tables, and internal links to relevant converters.
Length units
Guides for units used to measure distance, size, height, width, and physical dimensions.
Weight and mass units
Guides for units used to measure mass and everyday weight labels.
Temperature units
Guides for temperature scales, offset formulas, absolute temperature, and common real-world temperature references.
Pressure units
Guides for force per area, gauge pressure, absolute pressure, vacuum readings, and equipment pressure units.
Data storage units
Guides for bytes, decimal storage units, binary storage units, file size, and capacity labels.
Data transfer rate units
Guides for network speed, file-transfer rates, bit and byte notation, Mbps, and MB/s.
Power units
Guides for rate of energy transfer, motors, engines, appliances, HVAC power, watts, and horsepower.
How these pages are written
Each guide is written manually, with definitions, diagrams, comparison tables, formulas, common mistakes, and internal links to relevant converters.