Pool Evaporation (Water Loss) Calculator for Australia

Wondering how much water your pool is losing to evaporation? Find out using this pool water loss calculator! Enter your pool surface area, location and heating settings below to calculate your evaporation losses by month.

Pool Evaporation Rate Calculator

Evaporation rates by month

Evap Rate (mm)Total Evaporation (L)

Why Calculate Pool Water Loss?

There are a number of good reasons to calculate the water loss from your Australian swimming pool or spa.

Pool Cover Effectiveness

If you are thinking of buying a pool or spa cover, this calculator can give you a feel for how much water you might save once you install one.

As you can see from the calculations above, the water loss from evaporation can be substantial, so it can often make sense to get a pool cover, especially if you are facing water restrictions that impact how often you can fill up the pool.

Pool Heating Impact

If you have a pool heater or are thinking of purchasing one, you can use this calculator to see how much additional evaporation you are likely to get if you run your heater for a certain period of the year at a certain temperature.

You may be surprised by how much extra evaporation can be caused by running the heater at even a few degrees above normal pool temperature.

Sanity Check For Leaks

If you've noticed that your pool is losing a lot of water, you might be worried about whether you have a leak or not!

This calculator can help give you an idea of how much water loss is normal (due to evaporation).

If you are losing substantially more water than the calculator suggests, it might be worth looking into getting a leak detection expert to take a look at the structure of your pool, and confirming whether there is a leak present or not!

Bear in mind that warmer climates (like in Brisbane) tend to have greater evaporation than cooler climates.

How Much Water Do Pools Lose To Evaporation?

As an example, a typical 32m², unheated swimming pool located in Brisbane will lose around 62,400 L of water to evaporation over the course of a year.

This will sound like a lot, but bear in mind that this calculator doesn't consider rainfall, which will top up the pool and recover some of the losses to evaporation.

However in the drier months, there will be little rainfall and you will find yourself filling up the pool fairly often to make up for these losses.

If water restrictions are in place, there may be rules about filling up swimming pools, in which case it may make sense to invest in a pool cover.

How Often Should I Need To Add Water To My Pool?

If you have a typical 32m² unheated swimming pool, expect to lose about 5,000 L of water to evaporation per month.

If it doesn't rain for a week, you will lose about 1,000 L of water, meaning that you would need to run a standard garden hose (with a flow rate of 0.25 litres per second) for about 1 hour that week to recover the water losses.

Use this pool fill time calculator to work out how long it will take to fill your pool!

Data Source

This calculator uses humidity and pan evaporation data from the Bureau Of Meteorology (BOM). Data can be accessed from the BOM website.

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.