Above-ground pools are sized by diameter and wall height (for example 24 ft × 52 in), but they are normally filled to about 6 in below the top of the wall. Use the water depth, not the wall height, to dose chemicals correctly.
How to use the Round Pool Volume Calculator
- Diameter
- Water depth
- Fill flow rate
- Every result field is editable: type into Pool volume and Water depth plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the diameter, the water depth and your fill flow rate.
Common above-ground pools (48 in water depth)
| Diameter | US gallons | Litres |
|---|---|---|
| 12 ft | 3,384 | 12,810 |
| 15 ft | 5,288 | 20,016 |
| 18 ft | 7,614 | 28,823 |
| 21 ft | 10,364 | 39,231 |
| 24 ft | 13,536 | 51,241 |
| 27 ft | 17,132 | 64,852 |
| 30 ft | 21,151 | 80,064 |
| 33 ft | 25,592 | 96,877 |
Tips for an accurate estimate
- Measure inside dimensions of tanks and pools – wall thickness can change the volume noticeably.
- Use the average depth for pools with a sloping floor.
- Remember the weight: water weighs about 8.34 lb per US gallon (1 kg per litre), so large volumes need solid support.
- Check whether a figure is in US gallons, imperial gallons or litres before ordering chemicals or equipment.
Common mistakes to avoid
- Using wall height instead of water depth for above-ground pools.
- Assuming a horizontal tank’s volume is proportional to the liquid level – it is not.
- Mixing up flow units such as GPM, GPH and litres per minute.
Inputs explained
| Field | What to enter |
|---|---|
| Diameter | Units: ft, m, in, yd, cm |
| Water depth | Units: in, cm, mm, ft, m |
| Fill flow rate | Units: gpm, L/min, gph, m³/h, ft³/s, L/s |
What each result means
- Pool volume = pi×([Diameter]÷2)^2×[Water depth]
- Surface area = pi×([Diameter]÷2)^2
- Weight of water = [Pool volume]×1000
- Time to fill = [Pool volume]÷[Fill flow rate]
Formula
Volume = π × (D ÷ 2)² × water depthGallons ≈ D² × depth × 5.9 (feet)Worked example
Inputs — Diameter: 24 ft; Water depth: 48 in; Fill flow rate: 10 gpm.
Results — Pool volume = 13,536 US gal; Surface area = 452.4 ft²; Weight of water = 56.5 US ton; Time to fill = 22.6 h.
Frequently asked questions
How many gallons is a 24 ft round pool?
About 13,500 gallons at 48 in of water (52 in wall).
How many gallons in a 15 ft round pool 4 ft deep?
About 5,300 gallons.
Is the water depth the same as the wall height?
No – fill to about the middle of the skimmer, usually 6 in below the wall top.
What formula does the Round Pool Volume Calculator use?
Volume = π × (D ÷ 2)² × water depth.