How the converter works
Every unit in a category is stored as a factor relative to one base unit for that category, such as metres for length or grams for mass. To convert, the value is first expressed in the base unit, then re-expressed in the target unit.
This base-unit approach means any pair of units inside the same category works without needing a separate formula for each combination.
Choosing category and units
Pick the category first, because the From and To units must both belong to it. Trying to convert metres into kilograms is meaningless, and the tool will flag mismatched units.
- Length, mass, volume and area cover most everyday conversions.
- Speed, energy and pressure handle common engineering needs.
- The data category converts between bytes and larger digital units.
Practical tips
For repeated conversions in the same family, this saves looking up factors by hand and reduces arithmetic slips.
- Round only at the end to avoid accumulating small errors.
- For temperature, use the dedicated converter since it needs offsets, not just factors.
- Keep an eye on the unit label in the result so you read the right quantity.
Common mistakes
A "unit not valid" error almost always means the From or To unit does not match the selected category. Reselect the category, then choose units that belong to it.
Watch out for similar-looking units across categories, such as square metres versus cubic metres. Make sure the dimension matches what you actually want.
Formula
result = value · factor[from] / factor[to]Frequently asked questions
- Why did I get a "unit not valid" error?
- The From or To unit does not belong to the selected category. Pick a category and units that match (e.g. metres and feet for length).