Pool salt calculator

Enter the pool volume in litres, the current salinity in ppm, and the target salinity. The result is kilograms of salt to add, and how many 20 kg bags that is, rounded up. The inputs stay in the URL so the result can be shared.

Formula

Kilograms of salt to add = volume in litres × (target ppm − current ppm) ÷ 1,000,000. One part per million in pool water is one milligram per litre, so a 1 ppm rise in 1,000 litres is 1 gram. 20 kg bags = kilograms ÷ 20, rounded up. If current salinity is already at or above the target, the amount to add is 0 kg.

That factor is the same as 3.5 kg of salt per 1,000 litres when raising a pool from 0 ppm to 3,500 ppm, which is the start-up figure published by Crystal Aquatic Systems (a 50,000 litre pool needs about 175 kg). The 20 kg bag size is the unit used in Pool Pro's salt table.

Published chlorinator ranges differ. Pool Pro's how-to notes a broad band of 1,000 to 6,000 ppm and still tells owners to follow the chlorinator's manual. This page does not set a default target.

The volume calculator can fill litres here from its current result.