Group Activity:
Metrics Essentials

Simple Conversions to Memorize

Memorize the following metrics conversions. You should see a pattern that makes this relatively simple. In the end, you will memorize the list of metrics prefixes and a simple relationship between most neighboring pairs of units.

Here is how to set up a conversion between two metric units:

Memorize that there are 1,000 mm (millimeters) in 1 m (meter)
and create a conversion factor; then use it:
              1 m
4,350 mm × --------- = 4.35 m
            1,000 mm

Here are two examples of conversions between two metric units. These conversions require multiple steps.

Convert micrometers to meters:
              1 mm         1 m
650,000 µm × --------- × --------- = 0.65 m
             1,000 µm     1,000 mm

Convert liters to microliters
            1,000 mL     1,000 µL
0.00357 L × --------- × --------- = 3,570 µL
              1 L          1 mL

A helpful tip: When you convert from a larger unit (which is higher up on the chart) to a smaller unit then the answer should be a larger number. For example, 1.3 km is equal to 1,300 m. Also, when you convert from a smaller unit to a larger unit then the answer should be a smaller number. For example, 385 mm is equal to 0.385 m.

A Flexible Way to Create Conversions

If you memorize the information in the chart on the previous page, which is meant to be easy because nearly all of the conversions are based on the numbers 1 and 1,000, then you should be able to convert between any metrics prefixes. You will have to do so using multiple steps, however, if the units you are converting between are not right next to each other on the chart. It’s possible to create single conversions between units far apart on the chart. The text and examples below show you how.

Note: this section of the background information is optional. You can be completely successful in all metrics conversions without learning the following method.

To make a conversion factor from the metric units chart is easy. On the chart you will see that the unit prefixes all have a power of ten next to them. By counting the number of powers of ten between a pair of units on the chart you can tell how many of the smaller unit fit in one of the bigger unit. For example:

There are three powers of ten between the base unit (meter) and milli- (millimeter).
meter: 100           millimeter: 10-3    0 — (-3) = +3
103 = 1,000 so       1 m = 1,000 mm

Here’s how you do it, step-by-step:

1. Identify the pair of units you need a conversion factor for and decide which one is the bigger unit. The bigger unit is always the one closer to the top of the chart.
2. Write down the bigger unit’s abbreviation next to the number 1. This is how many of that unit will be in your conversion factor.
3. Figure out how many powers of ten separate the two units.
4. Write down 1 × 10^x next to the smaller unit’s abbreviation, where the x is the difference in powers of ten.

Here are two examples:

Create a conversion factor for kilograms to milligrams
kg: 10+3    mg: 10-3   kg is the bigger unit  so write: 1 kg = _____ mg     
do this: +3 — (-3) = +6   which means 1 × 106 mg   
so the conversion factor is 1 kg = 1 × 106 mg (1,000,000 mg)

Create a conversion factor for millimeters to micrometers
mm: 10-3    μm: 10-6   mm is the bigger unit  so write: 1 mm = _____ μm     
do this: -3 — (-6) = +3   which means 1 × 103 μm   
so the conversion factor is 1 mm = 1 × 103 μm (1,000 μm)

The answers should always give you a positive power of ten when you do it this way because you should always expect to have a large number of small units for each big unit.

One thing that is helpful to notice is that most of the prefixes are three powers of ten away from their two nearest neighbors. It becomes as easy as counting by 3s: 3, 6, 9, 12, etc. The only exception in the chart provided here is centi- which is 10^-2 and is one power of ten away from milli- and two powers of ten away from the base unit. So skip centi- most of the time (it’s only used for meters, anyway) and count by 3s.

Do the following exercises on a separate piece of paper. Number each problem carefully and clearly.

Simple Conversions

Convert each quantity into the unit shown. Each calculation will require only one conversion factor. Show work for the dimensional analysis calculation.

Show your work like this:

         1,000 μm
42 mm x --------- = 42,000 μm
          1 mm

Multi-step Conversions

Convert each quantity into the unit shown. Each calculation will require two or more conversion factors. Show work for the dimensional analysis calculation.

Optional: You may, if you wish, study the material in this document to learn how to make a single conversion factor between any pair of metric prefixes. If you do this, make sure the conversion factor is correct and write down the dimensional analysis conversion using your constructed conversion factor.

Show your work like this:

            1,000 μL   1,000 nL
0.054 mL x --------- x --------- = 54,000 nL
             1 mL         1 μL

Conversions without Dimensional Analysis

It is nearly always the case that when people learn the metric system they are taught how to count decimal places and how to move the decimal to convert from one metric prefix to another. This lesson does not do that because it is important for you to also know the actual conversions between units. Never again should you be unable to say how many cm are in a meter or how many mL there are in a liter.

Now you will do some conversions without writing them out but instead by ‘moving the decimal’ in your head. There is no explicit lesson for these exercises. The idea is for you to figure it out for yourself so that you truly understand it. For this set of problems write the given value and unit and an equal sign followed by the converted number with its new unit. The conversions will be between the same units as in the first section above with different numbers. Use this fact to help you to make sure you’re on the right track with your answers.

Show your work like this:

 32 mm = 0.032 m