About the Pool Volume Calculator
Knowing your pool's volume is the key to correct chemical doses, a properly sized pump and heater, and an estimate of how long it takes and how much it costs to fill. This calculator handles rectangular, round and oval pools. Enter the dimensions and the depths of the shallow and deep ends, and it takes the average depth to give the volume in litres, cubic metres, US gallons and UK gallons. If you tell it your hose flow rate in litres per minute, it also estimates how long the pool will take to fill.
Updated October 2026
How to use the Pool Volume Calculator
- 1Pick a rectangle, a round or an oval pool.
- 2Choose metres or feet.
- 3Enter the length and width, or the diameter for a round pool.
- 4Enter the depths at the shallow end and the deep end. Use the same number for a flat floor.
- 5Optional: enter your hose flow rate to see the fill time.
Measuring your pool
Measure the water surface, not the outside edge of the coping. Take depths at the shallow end, the deep end and the middle, and check that the floor slopes evenly. For an in-ground pool with a gradual slope the average of the two end depths is close enough for chemicals.
Round your result to the nearest thousand litres when reading product doses, since the measurements themselves are not precise.
Using the numbers
- Chlorine, balancer and algaecide doses are given per 10,000 litres or per 10,000 gallons.
- Heater size depends on volume and the temperature rise you want.
- Water costs: multiply the volume by your local water rate.
- Pump flow: aim to circulate the full volume in 6 to 8 hours.
- Cover size: add about 30 cm on every side.
More tools for the job
Use the Aquarium Volume Calculator for fish tanks, the Cylinder Calculator for tanks and barrels, the Concrete Calculator if you are building the shell and the Gravel Calculator for the base. The Unit Converter switches between litres, gallons and cubic metres.
Features
- Rectangle, round and oval shapes
- Litres, cubic metres, US and UK gallons
- Average depth for sloping floors
- Fill time from your hose flow
- Metres or feet
- Clear checks for missing sizes
Frequently asked questions
How do I calculate the volume of a rectangular pool?
Multiply length by width by average depth. A pool 8 m long, 4 m wide with depths from 1 m to 1.8 m has an average depth of 1.4 m and holds 8 × 4 × 1.4 = 44.8 cubic metres, or 44,800 litres.
How do I find the volume of a round pool?
Use pi times the radius squared times the depth. A round pool with a 4.5 m diameter and a flat depth of 1.2 m holds π × 2.25² × 1.2, about 19.1 cubic metres, or 19,100 litres.
What is the formula for an oval pool?
The surface area is pi times half the length times half the width, and the volume is that area times the average depth. This is the true ellipse formula, which is a little different from the common shortcut that multiplies length by width by 0.89.
How long will it take to fill my pool?
Divide the volume in litres by the hose flow in litres per minute, then convert to hours. A 44,800 litre pool at 20 litres per minute takes 2,240 minutes, which is about 37 hours.
Why do I need the volume?
Chemicals, algaecides, salt and heaters are all dosed by volume. Too little leaves the water unsafe, and too much wastes money and can irritate skin. A pump should turn the water over once every 6 to 8 hours.
Is the average depth always halfway?
Only when the floor slopes evenly. Pools with a hopper, a steep drop or a shallow shelf need a more careful estimate, for example by splitting the pool into sections and adding their volumes.