As discussed earlier, the amount of heat and time taken to heat a pool cannot be calculated accurately due to so many variables relating to heat loss from the surface, throught the floors and walls and evaporation coupled with solar gain.
The calculators below do however give an indication of these heat up times based on the pure calculations for the amount of heat required to heat a volume of water.

Calculate the time taken to heat a pool

Calculate size of heater required to heat a pool within a given time