Before rulers, people measured with their bodies. A foot was a foot. A cubit was elbow-to-fingertip. Try measuring your room two ways: hands first, then a ruler.
Type a value, pick units
0.3048
1 ft = 0.3048 m
Measure your room twice
- First, pace it out in feet (heel to toe) or hand-spans.
- Then measure with a ruler or tape in metres.
- Compare your two answers — they won't match exactly.
- That mismatch is exactly why the world standardised on the metre.
Since 1983, 1 metre is defined as the distance light travels in 1/299,792,458 of a second — identical for everyone, everywhere.
Your turn
Roughly how many of your feet (~25 cm each) fit in a 3 m wall?
Why standardised units matter
Your hand and mine are different sizes. Trade and engineering broke until we agreed on a metre. Today, the metre is defined by the speed of light — same for everyone, everywhere.
1 metre = the distance light travels in 1/299,792,458 of a second. Defined since 1983.