# Unit of length facts for kids

Kids Encyclopedia Facts

A unit of length is a way of measuring length or distance.

Common units of length in the International System of Units (SI) are:

But there are a lot of units that do not fit in the SI-System:

• fermi (fm) (= 1 femtometre in SI units)
• angstrom (Å) (= 100 picometres in SI units)
• micron (= 1 micrometre in SI units)
• Norwegian/Swedish mil (= 10,000 metres)

Common Imperial units and U.S. customary units of length include:

• inch (25.4 mm)
• mil (one thousandth of an inch, one thou)
• foot (0.3048 m, 12 inches)
• yard (0.9144 m)
• (terrestrial) mile (1609.344 m)

In addition, the following are used by mariners:

Surveyors in the United States continue to use:

• chain (~20.1m)
• rod (also called pole or perch) (~5 m)

Horse racing keeps alive:

Astronomical measure uses:

Physics also uses:

Old units of distance are:

In everyday conversation, and in informal literature, it is common to see lengths measured in units of objects of which everyone knows the approximate width. Common examples are:

• Football field (generally around 110 metres, depending on the country)
• Widths of a human hair (around 80 micrometres)

## Images for kids

Unit of length Facts for Kids. Kiddle Encyclopedia.