Lesson 15 — Activity 1:

Converting Imperial to Metric

To use the chart to convert an amount in one system to the other system, you need to FIRST find the conversion factor on the chart. You might remember from L14 — A2 that the conversion factor is the other unit that has a number different than 1 in front of it. This is the number that you will be multiplying by.

For example, in order to convert an amount in inches (which is an imperial unit) to an equivalent amount in centimetres (which is a metric unit), you would look at the imperial to metric side of the chart below (the left-hand side). Find the in to cm equivalent:

1 in = 2.54 cm 

The number 2.54 in front of cm is the conversion factor. MULTIPLY the original amount in inches by the conversion factor 2.54 and add the new unit, centimetres, to the answer. Let's try one!

Note: For these conversions and the ones that follow in the next lesson, you will want to use your calculator. Please get it ready now so you can practise converting the units.

Example: Convert 140 inches to centimetres.

Step 1: Look at the imperial to metric side of the chart (the left-hand side.)

Step 2: Find the inch to centimetre equivalent (1 in = 2.54 cm).

Step 3: Multiply the original amount (140 in) by the conversion factor (in this case, 2.54).

140 x 2.54 = 355.6 (which you can round up to 356).

140 inches is equal to 356 centimetres!

You have now converted an amount originally in inches, or imperial, to the equivalent amount in centimetres, or metric. It's just that easy!

Let's try some more examples!

Suppose you are a glazier (a person whose job it is to fit glass into windows and doors). You are preparing a window that is 12 feet long. If you are working from metric measurements on your blueprint, you might want to convert this length (12 feet, which is in imperial) to metres (which is in metric.)  

Since you want to convert an imperial measurement to a metric equivalent, use the imperial to metric side of the chart (the left-hand side) to find the conversion factor. Remember, the unit with 1 in front is the unit you are converting from. The unit with the conversion factor in front is the unit you are converting to. 

Example #1: Change 12 feet into metres. 

Look at the imperial to metric chart to find the line that shows feet to metres. The chart states that 1 foot = .305 metres, so .305 is the conversion factor.

12 x .305 = 3.66 — multiply the original amount of 12 feet by the conversion factor .305.

12 ft = 3.66 m

(Don't forget to place the metric unit, metres, after the answer.) 

Example #2: You are driving across the border to the US You buy some gas by the gallon, and you want to know how many litres that is. Convert 10 gallons into the metric equivalent in litres. 

Since you are converting an imperial amount, 10 gallons, to a metric unit, use the imperial to metric chart (the left-hand side).

The chart shows 1 gal = 4.56 L. Therefore, the conversion factor is 4.56.

10 x 4.56 = 45.6 — multiply the original amount of 10 gallons by the conversion factor 4.56.

10 gal = 45.6 litres

  Self-check!

Digging Deeper!