Step 1: How to make a chlorine solution from tablet or powder

We need to make: 0.5% chlorine, which is 5 mg/ml

We have: 5% chlorine solution, which is 50 mg/ml

50/5 = 10. So the 5% chlorine must be diluted to a 1:10 dilution

This means 1 part 5% chlorine solution to 9 parts water (not 10 parts of water because otherwise it would be 1:11 as the chlorine counts as a part)

Or a useful calculation is:

So for this answer: (5%/0.5%) - 1 = 10 – 1 = 9 parts of water needed

Step 2: How to make a 0.5% chlorine solution from a 5% chlorine solution

For example: If the label of calcium hypochlorite powder says that it has 70% available chlorine, and we would like to make one litre of 0.5% chlorine solution, a useful calculation is:

So that is: (0.5%/70%) x 1000 = 7.1 g per litre of water