The metric (SI) system uses powers of ten — every unit conversion is just moving the decimal point.
Quick check
What makes the metric system easy to compute with?
Why metric wins
- Conversions are ×10, ×100, ×1000 — no 12s, 16s or 5280s to memorise.
- One prefix set (kilo-, centi-, milli-...) works on every unit: km, kg, kL, kW.
- The whole world (bar a few holdouts) uses it, so science and trade share one language.
Your turn
Convert 4.2 km to metres without a calculator.
France adopted the metric system in 1799. Only the US, Liberia and Myanmar haven't fully switched — though scientists everywhere use it.
Adopted in France in 1799. The US is one of three countries that haven't fully switched to it (along with Liberia and Myanmar).