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Imperial units

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Imperial units

In a nutshell

The imperial unit system is another set of units that are not used as much nowadays, but are still seen in specific circumstances.

Imperial units

Here is a table of imperial units:




Inches, feet, yards, miles


Square inches, square feet, square miles


Cubic inches, cubic feet, gallons, pints


Ounces, pounds, stones, tons


Miles per hour (mph)

Note: Tons and tonnes are two different units of measure!

Converting between units

While there is no need to memorise any conversions related to imperial measurements, it is still important to be familiar with them when converting from either one imperial unit to another, or an imperial unit to a metric unit.

Example 1

A bird weighs 33​ pounds. Given that 11 pound =16=16 ounces, how much does the bird weigh in ounces?

The conversion rate is given:

11pound =16=16ounces

Multiply both sides by 33 to find what 33 pounds is equivalent to:

33pounds =16×3=16\times3 ounces

​​33 pounds =48=48 ounces

The bird weighs 48 ounces\underline{48 \ \text{ounces}}.

Example 2

Give an approximate conversion of 3030​ pints to gallons to 11​ decimal place, given that 11 litre 1.75\approx1.75 pints, and 11 gallon 4.5\approx4.5 litres.

First, convert the 3030​ pints to litres:

11litre 1.75\approx 1.75 pints

11pint 11.75\approx \frac{1}{1.75} litres

3030pints (11.75×30)\approx (\frac{1}{1.75}\times30) litres

3030pints 17.14\approx17.14 litres

Then, convert the 17.1417.14 litres to gallons:

11gallon 4.5\approx4.5 litres

11litre 14.5\approx \frac{1}{4.5} gallons

17.1417.14litres (14.5×17.14)\approx (\frac{1}{4.5}\times17.14) gallons

17.1417.14 litres 3.8095....\approx3.8095.... gallons

30 pints3.8 gallons (1.d.p)\underline{30 \ \text{pints} \approx3.8 \ \text{gallons} \ (1.d.p)}

Want to find out more? Check out these other lessons!

Converting between metric and imperial units

Frequently Asked Questions (FAQ)


  • Question: How do you convert imperial units to metric units or other imperial units?

    Answer: Use the conversion rate that you're given and multiply/divide your number by the conversion rate.

  • Question: What are imperial units?

    Answer: Imperial units are a lesser used set of units of measure.



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