Guides
Understand the measurement. Then convert it.
A calculator gives you a number. These guides help you read the original measurement, choose the right calculation and interpret the result.
How to read and compare land areas
Compare two plots, decode mixed-unit records and calculate the area of a simple shape.
Read the guide Reading dimensionsHow to read dimensions in inches and centimeters
Decode 5′ 8″ and 2½ in, convert every side and avoid rounding errors when checking a fit.
Read the guide Reading numbersMetric prefixes and decimal input
Tell centimeters from millimeters, avoid ambiguous decimal separators and round only after comparing the quantities.
Read the guide TemperatureCelsius, Fahrenheit and Kelvin
Convert a reading such as 25 °C, calculate a temperature change and understand the absolute-zero check.
Read the guide Choosing the calculationLength, area or volume?
Work out whether to convert an edge, a surface or a capacity, with room and storage-box examples.
Read the guideFrom a practical question to the right calculation
These guides are not catalogs of every conversion factor. Each tackles a task that takes more than one multiplication: mixed-unit area records, area versus shape, feet with remaining inches, or comparing several dimensions of an item.
If you have a number and know both units, go straight to a converter. If you are unsure how to read the original measurement, choose a guide above. Each shows its working, assumptions and common mistakes.