Metric 101 - Reference Points

Learning metric really only requires a few reference points and a way to use them in everyday life. It is up to you which things you want to start with first, whether you want to understand Celsius temperatures, or distances, or weight measures, etc.

It might help to buy some measuring devices. For example, to help you use metric units, you might get a Celsius weather thermometer, a kilogram bathroom scale, a liter water bottle, and a meter stick. If you bike, you can get a bike computer, which will show speed and distance using kilometers if you set it to do so (available at any bike shop). Scales and weather sensors are easily available at Walmart or Target. Meter sticks are available on Amazon and elsewhere.

If you haven't looked at it yet, see the page about how to learn the metric system.

Temperature - Degrees Celsius

To understand Celsius temperatures just remember:

Thirty's warm,
Twenty's nice,
Ten's cold,
Zero's ice.

That rhyme will get you 80% of the way. For extra credit, you can remember that the boiling point of water is 100 °C and body temperature is 37 °C.


Can there be any doubt that millimeters make far more sense for small distances than fractions of an inch? Only a masochist would want to compare "three-eights inch" to "nine-sixteenths of an inch".

For slightly larger sizes you can use centimeters or stick with millimeters. Distances you can walk would be measured in meters, or kilometers if you really need the exercise. Here are a few reference points, but you will want to add your own as well.

Width of a pencil 6 or 7 millimeters
Length of a pencil 10 to 20 centimeters
Height of a doorknob 1 meter
Width of your living room Go measure it! It could be 4 meters or 6 or more.
Length of your commute Try using to find the answer.
New York to LA 4000 kilometers by air


Weights you can hold in your hand range from grams to kilograms. Once you get into thousands of kilograms (think car-size weights), you might switch to metric tons, also known as tonnes. The word "tonne" is not simply a British spelling of ton, it means a metric ton, which is one thousand kilograms.

Nickel coin 5 grams
An egg 50 grams
Can of peaches 450 grams
Full water bottle, 1 liter 1 kilogram
Newborn baby 2.5 - 4.0 kg
Lightweight adult 50 - 70 kg
Medium-weight adult 70 - 100 kg
Really big football player 140 kg
Horse Several hundred kilograms
Honda Civic 1250 kg
Transit bus 8 to 20 tonnes, depending on how big


Small volumes (such as in a drinking glass) can be measured in milliliters. Buckets may hold tens of liters, and ponds may hold hundreds or thousands of cubic meters.

Sip of water A few milliliters
Glass of water 200 to 300 milliliters
Small office trash can 10 to 15 liters
Large trash can with wheels 250 to 400 liters

Did you know that one millimeter of water covering one square meter adds up to exactly one liter? There are close relationships between volume and length measurements.

Next: Why Metric? >>