When to use it
For converting units of length, weight, temperature, and time. Whichever row you type in, the other units in the same category update instantly. "How many miles is 300 km?" and "How many km is 480 miles?" are the same action.
Decimals
The decimal-places control (2 · 4 · 6 · 10) only affects display. Internal precision stays at full regardless. Very large or very small values auto-switch to scientific notation (e.g. 1.5e-7).
Why temperature is different
Length, weight, and time share a common zero — you convert by multiplying (1 km = 1000 m). Temperature is different: 0°C and 0°F are different points. Conversion needs a formula, not just a factor. This tool anchors on Celsius and converts Fahrenheit and Kelvin both ways.
Supported units
- Length — millimeter · centimeter · meter · kilometer · inch · foot · yard · mile
- Weight — milligram · gram · kilogram · tonne · ounce · pound
- Temperature — Celsius · Fahrenheit · Kelvin
- Time — millisecond · second · minute · hour · day · week
Conversion is pure arithmetic
Length · weight · temperature · time across 23 units. Conversion factors are numerical literals in the code — no fetch, no telemetry. Inputs and units stay in the page.