Guideline Index

Appendix B – Explanatory Notes on the Metric System

Often people do not realise the connections between the units in the metric system. The meaning of the prefixes centi and milli, which should make the system easy to use, are lost on many adults who have never had the opportunity to learn about or discuss the new system. Many people will buy 600 mL of milk without ever realising that mL is an abbreviation of millilitre or that it is in any way connected to a litre measure.

A prefix at the start of a word often gives a clue to the meaning of the word. The prefix is a short descriptive word or abbreviation at the beginning of a word that adds to or qualifies its meaning.

A word like cent means one hundred , for example:

Cent: 100 cents in a dollar
Century: 100 years in a century100 runs in a century in cricket
Centipede: 100 legs on a centipede.

Once this use of the prefix is understood the use of milli, as a thousandth part (1/1000) is easier to comprehend. Words like millimetre, millilitre and milligram all suddenly start to make sense.

Millimetre : one thousandth of a metre. There are 1000 millimetres in one metre.
Millilitre : one thousandth of a litre. There are 1000 millilitres in one litre.
Milligram: one thousandth of a gram. There are 1000 milligrams in one gram.

Another common prefix is kilo. This is a prefix for one thousand. So therefore a:

Kilometre: is 1000 metres.
Kilogram: is 1000 grams.
Kilolitre: is 1000 litres.

Other common prefixes to describe other measurements that farmers use are:

Mega: one million. A megalitre is a million litres or a megajoule is one million joules.
Hecto: Ten thousand (10,000). A hectare is 10,000 square metres, or a 100-metre by 100-metre square.

Some common conversions from Imperial to metric are:

  • 2.47 acres = 1 hectare.
  • 1 acre = 0.405 hectare.
  • 0.39 inches = 1 centimetre.
  • 1 inch = 2.54 centimetres.
  • 39.37 inches = 1 metre.
  • 1.09 yards = 1 metre.
  • 1 yard = 0.914 metres.
  • 0.621 miles = 1 kilometre.
  • 1 mile = 1.61 kilometres.

Thinking Metric

For farmers who have grown up with the Imperial system one of the most important things to concentrate on is the ability to think metric. It is far less confusing if you can try to think in metric terms, the prefixes help you with how big or small the measurement is and you don’t have to continually convert from one system to another. The of the most effective ways to think metric is to think of objects you know well as a reference point. For example, the length of your road might be close to 1 kilometre or you can visualise a milk carton as 1 litre or a plastic chemical drum as 25 litres. If you can begin to visualise other measures in the same way, and try to use them as often as you can then you’re well on your to thinking metric.