How to do metric conversions:
There are many occasions when it is necessary to convert one unit of measurement to another when undertaking drug calculations.
The metric system is based on a number of basic measures or units e.g.
Quantity |
Unit |
Symbol |
length |
metre |
m |
mass |
gram |
g |
volume |
litre |
l |
time |
second |
s |
Large and small quantities of these units often have a prefix to make writing quantities more compact for example 0.000001g may be written as 1 mcg or 1µg.
Some common units of measurement are:
Prefix symbol multiplication factor
Prefix |
Symbol |
Multiplication Factor |
mega |
M |
1,000,000 |
kilo |
k |
1,000 |
hecto |
h |
100 |
deka |
da |
10 |
Unit |
e.g. g, m, l or s |
1 |
deci |
d |
0.1 |
centi |
c |
0.01 |
milli |
m |
0.001 |
micro |
mcg or µ |
0.000001 |
Converting a number from one metric unit to another involves moving the decimal place to the left or the right.
To work out how many decimal places to move:
Example 1:
Convert 0.1 grams to milligrams.
The decimal place is moved 3 places to the right.
Mg - - kg hg dag g dg cg mg - - µg
0.1 g = 100 mg
Example 2:
Convert 375 millilitres to litres.
The decimal place is moved 3 places to the left.
Ml - - kl hl dal l dl cl ml - - µl
375 ml = 0.375 l