The two mistakes behind almost every conversion error
The first is rounding too early. Converting 26 miles through “1 mile ≈ 1.6 km” gives 41.6 km; the exact factor 1.609344 gives 41.84 km — a 240-meter error that would misplace a marathon finish line. The rule: convert with full precision, round only the final number to the precision the context needs. This tool applies exactly that discipline internally.
The second is confusing mass and weight units with force, or dry and fluid measures. A “fluid ounce” is a volume (about 29.6 mL); an “ounce” is a mass (about 28.3 g); they are unrelated despite the shared name, and recipes mix them freely. When a conversion looks surprising, check whether the two units actually measure the same physical quantity — the category tabs in the converter enforce this automatically, which is itself a quiet form of error prevention.
Where each category shows up in practice
- Length — screen sizes are sold in inches everywhere, apartment listings in m² or ft² depending on the market, running distances in km or miles. The cm↔inch pair alone covers monitors, TVs, phone screens, and furniture.
- Weight — international shipping quotes in kg, US shipping in lb; gym plates differ by continent; recipe portions swing between grams and ounces.
- Temperature — the 37 °C / 98.6 °F body-temperature pair and the oven range (180 °C = 356 °F) are the two conversions people look up most; the reference table in the tool includes both anchors.
- Data — the decimal-vs-binary split explains the eternal “missing gigabytes” complaint: a 1 TB drive holds 10¹² bytes, which Windows reports as 931 GiB using binary units. Neither number is wrong; they are different units wearing similar names.
Related tools on this site
For conversions this tool deliberately does not cover: Currency Converter handles money (rates change daily, unlike physical constants), CSS Units Converter handles px/rem/em for web work, and Timezone Converter handles the one everyday conversion where arithmetic alone fails — time.