Metric Conversion & Metric System

This page offers information on the metric system and metric conversion. The following related pages may also be of interest:

For accuracy, the converters below use the official conversion rates (which are up to 13 digits). However, for ease of use, the reference table (chart) under each converter rounds off to the nearest 2nd digit.

Length Conversion

For length, there is no difference between USA and Imperial measures.



Imperial/USA unit

Metric (SI) unit


Metric (SI) unit

Imperial/USA unit


2.54 centimeters



0.39 inches


30.48 centimeters



3.28 feet


0.91 meters



1.09 yards


1.61 kilometers



0.62 miles

Weight (or mass) conversion



Imperial/USA unit    

Metric (SI) unit


Metric (SI) unit

Imperial/USA unit

Ounce (weight)

28.35 grams



0.035 ounces


0.45 kilograms



2.21 pounds

UK ton (2240 pounds)

1.02 metric tons


Metric ton (1000 kg.)

0.98 UK tons

US ton (2000 pounds)

0.91 metric tons


Metric ton (1000 kg.)

1.10 US tons

The USA and Imperial systems of measurement use the same ounce and pound. The USA ton (also known as the "short ton" is 2000 pounds, the UK ton (also known as the "long ton") is 2240 pounds, and the metric ton is 1000 kg.

In the metric (SI) system, the term mass is used instead of weight. Weight is a measure of how heavy something is, whereas mass is a measure of the amount of matter. To illustrate, something that weighs 60 pounds on the earth would only weigh about 10 pounds on the moon (due to the lower gravity of the moon), whereas something the has a mass of 60 Kilograms on the earth would still have a mass of 60 kilograms on the moon (as the amount of matter is unchanged). Consequently, the statement that 1 kilogram is 2.21 pounds is true here on earth but not elsewhere (a point mainly of interest to scientists).

Temperature Conversion


The USA and Imperial systems measure temperature using the Fahrenheit system. The Metric (SI) system originally used the Celsius temperature system, but now officially uses the Kelvin temperature system. However, few people aside from scientists have switched to the Kelvin system and the Celsius system is almost always used by most people for ordinary (non-scientific) purposes. The above converter handles Fahrenheit, Kelvin and Celsius but since the Celsius system is more commonly used than the Kelvin, we provide the following comparison of the Fahrenheit and Celsius systems::

  • The freezing point of water in Fahrenheit is 32 degrees, in Celsius it is 0 degrees.
  • The boiling point of water in Fahrenheit is 212 degrees, in Celsius it is 100 degrees.
  • Consequently the difference between freezing and boiling is 180 degrees Fahrenheit (212-32) or 100 degrees Celsius (100-0). This means that 180 degrees change in Fahrenheit is equal to 100 degree change in Celsius, or more simply 1.8 degrees Fahrenheit equals 1.0 degrees Celsius.

This gives rise to the following equations to convert between Celsius and Fahrenheit:

  • °C = (°F - 32) ÷ 1.8        For example: (68°F-32) ÷ 1.8 = (36) ÷ 1.8 = 20°C
  • °F = (°C x 1.8) + 32       For example: (20°C x 1.8) + 32 = (36) + 32  = 68°F  

Some common examples are:

  • Freezing = 0 °C , 32°F
  • Room temperature = 20 °C , 68°F
  • Normal body temperature = 37 °C , 98.6°F
  • A very hot day = 40 °C , 104°F
  • Boiling point of water = 100 °C , 212°F

Area Conversion

For area, their is no difference between USA and Imperial measures.


Imperial/USA unit   

Metric (SI) unit


Metric (SI) unit

Imperial/USA unit


0.40 hectare



2.47 acres

Square inch

6.45 square centimeters


Square centimeter

0.16 square inches

Square foot

0.09 square meters


Square meter


Square yard

0.84 square meters


Square meter

1.20 square yards

Square mile

2.60 square kilometers


Square kilometer

0.39 square miles

Cubic foot

0.028 cubic meters


Cubic meter

35.23 cubic feet

Cubic yard

0.76 cubic meters


Cubic meter

1.35 cubic yards


 Volume (or Capacity) Conversion



Imperial/USA unit

Metric (SI) unit


Metric (SI) unit

Imperial/USA unit

Teaspoon (UK)

5.92 milliliters



0.17 teaspoons (UK)

Teaspoon (US)

4.93 milliliters


0.20 teaspoons (US)

Tablespoon (UK)

17.76 milliliters


10 Millilitre

0.56 tablespoons (UK)

Tablespoon (US)

14.79 milliliters


0.68 tablespoons (US)

Fluid ounce (UK)

28.41 milliliters


100 millilitre

3.52 fluid ounces (UK)

Fluid ounce (US)

29.57 milliliters


3.38 fluid ounces (US)

Pint (UK)

0.57 liters



1.76 pints (UK)

Pint (US)

0.47 liters


2.11 pints (US)

Quart (UK)

1.14 liters


0.88 quarts (UK)

Quart (US)

0.95 liters


1.06 quarts (US)

Gallon (UK)

4.55 liters


0.22 gallon (UK)

Gallon (US)

3.79 liters


0.26 gallons (US)

Measures of volume are different for the two systems due to the Imperial ounce being slightly smaller than the US equivalent (which affects all multiples of the ounce), and also due to the UK pint having 20 ounces whereas the the US pint has only 16 ounces.

The sizes of the smaller Imperial measures (teaspoon and tablespoon) are open to interpretation. See Cooking converter for further information on these measures.

 Mileage Conversion



Energy Conversion



Force Conversion 


Power Conversion


 Pressure Conversion



 Additional References

The following provide additional information on the metric system and conversion to the metric system:

UK Metric Association

US Metric Association

International Bureau of weights and measures

The original SW for the converters was kindly made available by www.metric4us.com, but has been substantially modified by us (for example, to include both USA and Imperial measures).

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