MyCalculatorNow resource guide
Conversions and Precision
Choose the right unit, preserve significant precision, and avoid mixing length, area, mass, and temperature.
Overview
A conversion changes how a quantity is expressed, not the quantity itself. Keep the dimension, named standard, and measurement precision visible.
Convert through a common reference unit
For compatible linear units, output=input×source factor÷destination factor. The international inch is exactly 0.0254 meters, so 12 inches is exactly 0.3048 meters as a defined conversion. The measured board itself may not be known exactly. Keep length with length, mass with mass, and time with time; a conversion cannot turn a length into an area without additional geometry.
Square or cube geometric factors
A foot contains 12 inches, but a square foot contains 12²=144 square inches and a cubic foot contains 12³=1,728 cubic inches. For construction volume, 27 cubic feet make a cubic yard because a yard is 3 feet in each dimension. This is why applying a length conversion factor directly to an area or volume can create a large error. Label the quantity before selecting a converter.
Handle temperature offsets correctly
Absolute temperature uses both a scale and an offset: °F=°C×9/5+32 and K=°C+273.15. Thus 20°C is 68°F, while an increase of 20°C is an increase of 36°F. The temperature-interval tool deliberately has no 32-degree offset. Do not substitute an interval conversion for an absolute-temperature conversion in recipes, reports, or engineering calculations.
Check similarly named standards
US and Imperial gallons are different volumes. A decimal kilobyte is 1,000 bytes, while a kibibyte is 1,024 bytes. A lower-case b can mean bit while upper-case B means byte; one byte contains eight bits. Mass is not force, and power in watts is not energy in watt-hours. Read the entire unit label rather than relying on a familiar abbreviation.
Keep meaningful precision
A unit conversion cannot create information absent from the measurement. A length recorded to the nearest centimeter should not be reported with many implied millimeter digits just because the converter displays them. Retain extra digits for intermediate arithmetic, then round the final result to suit the original precision. Save the original quantity and both unit labels so another person can reproduce the conversion.
Use results responsibly
Calculations are educational estimates. Keep your units and inputs visible, check important results against authoritative sources, and seek qualified professional advice for decisions involving health, money, law, construction, or safety.