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How Do You Convert Imperial to Metric?

When you convert imperial units to metric units, you need to multiply each unit by a conversion factor. This entry gives you an overview of which conversion factor to use and which metric unit it produces.


The most common imperial length unit outside of the US is inches. PC monitors and TV sizes are measured in inches. You could for example read in a store that a PC monitor is 24 inches or 24”. What does that mean? It means that the diagonal of the monitor is 24 inches long.

Monitor measuring 24 inches along the diagonal

So how long is that? That’s what you’ll learn in this entry.

For length you usually convert inches to centimeters, feet to centimeters, yards to meters and miles to kilometers or meters.

Imperial Unit

Conversion Factor

Metric Unit

1 in


2.54cm 2.5cm

1 ft


30.48cm 30cm

1 yd


0.9144m 0.9m

1 mi


1609.3m 1.6km

Example 1

So how many centimeters is the 24” monitor?

You find the conversion factor from the table above to be 2.54:

24in 2.54 = 60.96cm.

Meaning the monitor has a diagonal which is 60.96 cm.

Example 2

An American football field is exactly 100 yards. How long is that in meters?

You find the conversion factor from the table above to be 0.9144:

100yd 0.9144 = 91.44m.


For area you usually convert square inches to square centimeters, square feet to square centimeters, square yards to square meters, acres to square meters and square miles to square kilometers.

Imperial Unit

Conversion Factor

Metric Unit

1 in2


6.4516cm2 6.5cm2

1 ft2


929cm2 0.09m2

1 yd2


0.8361m2 0.8m2

1 acre


4046.9m2 4047m2

1 mi2


2.59km2 2.6km2

Example 3

You measure you room to be 13 feet long and 8 feet wide. What is the area of your room in square feet and square meters?

Square feet:

13ft 8ft = 104ft2

Square meters:

You use the table and see that you need to multiply with 929 to get square centimeters, but since you want square meters, you multiply with 929 1 100 = 0.0929:

104ft2 0.0929 = 9.6616m2.


For volume you usually convert fluid ounces to milliliters, pints to liters and gallons to liters.

Imperial Unit

Conversion Factor

Metric Unit

1 fl oz


29.574mL 30mL

1 pt


0.4732L 0.5L

1 gal


3.7854L 3.8L

Example 4

You travel to Germany where the soda bottle says 0.5L. You remember that a bottle of similar size in USA is 20fl oz. Which bottle has more soda?

You need to find out how many liters 20 fl oz is:

20fl oz 29.574 591.5mL 0.59L.

Seems like the bottles in USA has more soda in them than the ones in Germany. The saying “everything is bigger in America” is true in this case.


You usually convert ounces to grams, pounds to kilograms and ton to metric tonne.

Imperial Unit

Conversion Factor

Metric Unit

1 oz


28.35g 28g

1 lb


0.4536kg 0.45kg

1 ton


0.9072tonne 0.9tonne

Example 5

Your dog weighs 45lb. How much is that in kilograms?

The table above gives

45lb 0.4536 20.4kg.

Good boy!

Mass Density

Since density consist of two units, you can convert each of them separately and then combine them. Density in imperial is given by lb/ft3, while metric often uses g/cm3. You can convert lb/ft3 to g/cm3 by first converting pounds to grams and then feet to centimeters. One foot is 0.3048 meters, so one foot cubed is 0.30483 = 0.0283m3: 1lb = 453.6g 1ft3 = 0.0283m3 = 28300cm3 1lb/ft3 = 453.6g 28300cm3 = 0.016g/cm3


You convert from lb/ft3 to g/cm3 by multiplying lb/ft3 with 0.016.


The US uses Fahrenheit, while most other countries use Celsius. Unlike most other units, you cannot multiply Fahrenheit with a conversion factor to get Celsius. Instead, you have to use this simple formula:


°C is temperature measured in Celsius and °F is temperature measured in Fahrenheit.

°C = °F 32 1.8

Example 6

On a hot summer day, it’s 108°F outside. What is that in Celsius?

You use the above formula:

108 32 1.8 = 76 1.8 42.2°C.
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How Do You Convert Metric to Imperial?