The tried and tested method.

When I talk to nurses and nurse educators about the calculations that cause most difficulty, they usually say the same thing.

Unit conversions.

You will need to be able to convert both units of weight (kilograms, grams, milligrams and things like that) and units of measure (litres and millilitres).

The beauty about all of these calculations is that the scale factor is the same every time.

Look at these conversions, and you will see for yourself.

- 1 kilogram = 1000 grams.
- 1 gram = 1000 milligrams.
- 1 milligram = 1000 micrograms.
- 1 microgram = 1000 nanograms.
- 1 litre = 1000 millilitres.

See what I mean - each of these units is worth a thousand of the unit below. Which means that if you want to convert from the bigger unit into the smaller unit, then what you need to do is times the number by 1000 (and similarly, to convert from the smaller unit to the bigger one you would divide it by 1000).

(Plus your free practice tests if you haven't already received them)

So you need to multiply (or divide) your numbers by 1000. What's the easiest way of doing it?

The truth is that different people teach it different ways. Some would argue that you should 'bounce' the decimal point three places. Other suggest that you should move each digit.

Which should you do?

That said, when I teach this, I will always suggest moving the numbers, for one simple reason - I want you to actually understand what you are doing, not just follow some trick that you have learned but don't get.

So, the Maths For Nurses Unit Conversions method is to move the numbers. Let me show you why this works with an example. I want to convert 3.65 litres into millilitres.

So, what have I done here?

I have lined up the numbers according to their place value (hundreds, tens, units, etc.), and I know that the conversion is 1 litre = 1000 millilitres, so I move the number from the 1s (which in this case is 3) into the 1000s. The other digits follow it like a chain, and then I can fill in the space that is left with a zero.

3.65 litres is 3650 millilitres, and doing it this way makes it visually very clear from the conversion factor of 1 litre = 1000 millilitres (in a way that moving the decimal point just wouldn't).

The same method works equally well for dividing. If I want to convert 7200g in kilograms, I am moving from a smaller unit to a larger one, so I need to divide by the conversion factor of 1000.

To do this, I just need to move the digit in the thousands column (the 7) into the 1s

If you would like more tips and advice on Maths For Nurses unit conversions, as well as practice questions to try, enter your email address below and I will send you the Unit Conversions chapter of my Maths For Nurses book, as well as a few practice drug calculation tests.

(Plus your free practice tests if you haven't already received them)