An average a 3.7 by 7.3 metre in-ground backyard pool holds about 45,000 litres of water. As a rough estimate, you would need 1kg of shock for every 45 000 litres of water.
Our Hy-Clor Super Shock is available in 500g, 2 kg, 4 kg, and 10 kg. So for a 45,000 litre pool, you would need two 500g bags or tubs of our shock treatment, or half of the 4kg bucket.
The exact number of bags of shock you need to winterise your pool depends on the size of your pool, the current condition of your pool water, and the brand of shock.