Metric is easy to use

It's simple and consistent

All metric units have multiples that are powers of ten, i.e. 10, 100, 1 000 and so on. So to convert between units of different sizes, you need only move the decimal point:

1.234 m = 123.4 cm = 1 234 mm

The relationship between different units is far simpler than in imperial:

Calculations take a single step

Suppose we want to find how much paint is needed to cover a wall. The wall's measurements are either 4.37 m long and 2.39 m high, or 14 feet 4 inches by 7 feet 10 inches; what's its area?

Metric case

The decimal basis of metric means we can find the answer straight away (with the aid of a calculator) as 4.37 x 2.39 = 10.4443 or approximately 10.4 m².

Imperial case

Now we have to multiply 14 feet 4 inches by 7 feet 10 inches to get the result in square feet.

We can't do this directly without either converting to inches or decimalising the measurements in feet. Either way requires extra arithmetic:

14 feet 4 inches = (14 x 12) + 4 = 172 inches

7 feet 10 inches = (7 x 12) + 10 = 94 inches

Then 172 x 94 = 16 168 sq inches = 16 168 ÷ 144 = 112.278 or approximately 112 square feet.

Alternatively:

4 inches = 4 ÷ 12 = 0.333 feet

10 inches = 10 ÷ 12 = 0.833 feet

14.333 x 7.833 = 112.271 or approximately 112 square feet.

You might object that working in feet alone is, roughly, accurate. But why not choose a simpler, more direct method - metric - that allows any degree of precision?