Centimetric ruler/measuring tape

2010-07-03 08:52:46 UTC

One mistake a lot of people make when trying to learn the metric system is trying to memorize and use conversion factors. Do you think people in other countries measure everything in inches and then convert to centimeters?

No, they have measuring tapes and rulers in centimeters or millimeters. Such rulers are easy to come by here in the US, but the measuring tapes are not.

So, in order to solve that problem and make it easier for fellow Americans to measure lengths in metric units, I present my Centimetric Ruler. It totals 2.5 meters, and looks like this:

Despite the name, I use it as a measuring tape, coiled up and held in that shape (when not in use) by a small rubber band.

The page is US Letter (because that’s the paper I have), and you’ll need to cut out the pieces and tape them together. I recommend cutting through the tick marks so that there is no gap between them and the bottom of the “tape”.

Note that every 25th centimeter appears twice in the printout. This is to give you one centimeter in which to lay each segment over the previous/next one.

There’s nothing I can do for you for measuring mass (but scales that measure in grams are easy to come by; you can buy a digital one at Target for \$20), but volume is easy, and demonstrates the elegance of the metric system pretty well:

1. A liter is equal to the volume of a cube that is 1 decimeter (= ¹⁄₁₀ meter = 10 cm) to a side. That volume is 1 dm × 1 dm × 1 dm, or 1 dm³—one cubic decimeter.
2. ¹⁄₁₀ of a decimeter is one centimeter (¹⁄₁₀₀ of a meter).
3. Imagine, or construct, a cube one decimeter to a side. Starting from one corner, make a cut in each edge, one-tenth of the way from the corner. This will produce a cube that is one centimeter to a side—one cubic centimeter.
4. Note that this cube is ¹⁄₁₀ of the larger cube in each dimension, which means its volume is (¹⁄₁₀ × ¹⁄₁₀ × ¹⁄₁₀) = ¹⁄₁₀₀₀ of the volume of the larger cube.
5. The volume of the larger cube being one liter, the volume of the smaller cube is ¹⁄₁₀₀₀ of that. ¹⁄₁₀₀₀ of a liter. One milliliter.
6. QED: One cubic centimeter (1 cc) = one milliliter (1 ml).

Knowing how volume and length relate to each other in metric, you can use the measuring tape (most easily on cuboid objects) to measure volume as well.

3 Responses to “Centimetric ruler/measuring tape”

1. Luke Says:

For mass, if you are measuring liquids that are primarily water (eg Milk) based 1 litre of water == 1kg. 1 cubic centimeter == 1 gram. Of course liquids mass/volume can change depending on temp etc.

2. Peter Hosey Says:

1 liter of water is not 1 kg, nor is 1 cc (1 ml) 1 gram. They’re closest for 40-ish °F (4°C) water, but never equal—1 liter is always at least a little less than 1 kg.

3. Jon H Says:

FYI: Many/most US inch measuring tapes have centimeters on the other side, like this one: http://www.amazon.com/MABIS-DMI-Healthcare-35-780-010-Measure/dp/B001BJO22Q/ref=sr_1_6?ie=UTF8&qid=1291865155&sr=8-6

Do not delete the second sentence.