Inches, Feet and Miles

A new television is sold as "55 inches". A pilot says the plane is flying at "35,000 feet". A road sign in the United Kingdom says "London 20 miles". The metre has been around for more than 200 years, so why are these older units still here?

The units that stayed

In the Your Foot, My Foot lesson we saw that people first measured with their bodies. Some of those units were tidied up and kept, especially in Britain and the countries that learned them from Britain:

• the inch - at first about the width of a thumb;
• the foot - 12 inches;
• the yard - 3 feet;
• the mile - 1,760 yards, at first a thousand paces of a Roman soldier (counting a pace as two steps).

Notice the strange numbers: 12, 3 and 1,760. With metres, everything goes in tens: 10 millimetres, 100 centimetres, 1,000 metres. With these older units, you have to remember a different number at each step.

Today most countries use metres. The United States still uses inches, feet and miles in everyday life. The United Kingdom uses miles on road signs, and many people there give their height in feet and inches. And all over the world, screens are sold in inches and most aeroplanes give their height in feet.

How they compare

Since 1959, these units have been fixed using the metre. An inch is exactly 2.54 centimetres. You don't need to remember that number; rough rules are enough:

• 1 inch is about 2 and a half centimetres;
• 1 foot is about 30 centimetres - the length of a long school ruler;
• 1 yard is a bit less than 1 metre;
• 1 mile is about 1.6 kilometres - a bit more than one and a half.

So when the road sign says 20 miles, you know it is about 32 kilometres. And the 55-inch television? Its screen, measured from one corner to the opposite corner, is about 140 cm.

Try it at home

1. Many rulers have centimetres on one edge and inches on the other. Find one.
2. Check that 1 inch reaches about two and a half centimetres.
3. Measure your height in centimetres, then in feet and inches. Which number is easier to say?

Words to know

• inch - an older unit of length, exactly 2.54 cm
• foot - 12 inches, about 30 cm
• yard - 3 feet, a bit less than a metre
• mile - 1,760 yards, about 1.6 km

Big idea

Inches, feet, yards and miles are older units, still used in the United States and in some places elsewhere. They don't go in tens, but rough rules connect them to metric units: an inch is about 2.5 cm, a foot about 30 cm, and a mile about 1.6 km.