You need the pool volume to dose chemicals correctly, size the pump and filter, and estimate the cost and time to fill it. Pools with a sloping floor are approximated by their average depth.
How to use the Pool Calculator
- Pool shape
- Length
- Width (kidney: wide end A)
- Kidney narrow end B
- Shallow end depth
- Deep end depth
- Water price
- Fill flow rate
- Every result field is editable: type into Pool volume and Deep end 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
Choose the pool shape and enter its dimensions, shallow and deep end depths, the price of water and the flow of your hose or fill line.
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 |
|---|---|
| Pool shape | Choose one: Rectangle, Round (length = diameter), Oval, Kidney |
| Length | Units: ft, m, in, yd, cm |
| Width (kidney: wide end A) | Units: ft, m, in, yd, cm |
| Kidney narrow end B | Units: ft, m, in, yd, cm |
| Shallow end depth | Units: ft, m, in, yd, cm |
| Deep end depth | Units: ft, m, in, yd, cm |
| Water price | Units: /1000 gal, /m³ |
| Fill flow rate | Units: gpm, L/min, gph, m³/h, ft³/s, L/s |
What each result means
- Average depth = ([Shallow end depth] + [Deep end depth])÷2
- Pool volume = [Surface area]×[Average depth]
- Weight of water = [Pool volume]×1000
- Cost to fill = [Pool volume]×[Water price]
- Time to fill = [Pool volume]÷[Fill flow rate]
Example values
How the main result changes when Deep end depth changes and everything else stays at the example values above:
| Deep end depth (ft) | Pool volume (US gal) |
|---|---|
| 4 | 14,363 |
| 6 | 18,193 |
| 8 | 22,023 |
| 10 | 25,853 |
| 12 | 29,683 |
| 16 | 37,343 |
Formula
Average depth = (shallow + deep) ÷ 2Volume = surface area × average depthKidney area ≈ 0.45 × (A + B) × L; oval area = π/4 × L × WWorked example
Inputs — Pool shape: Rectangle; Length: 32 ft; Width (kidney: wide end A): 16 ft; Kidney narrow end B: 10 ft; Shallow end depth: 3.5 ft; Deep end depth: 8 ft; Water price: $5 /1000 gal; Fill flow rate: 10 gpm.
Results — Surface area = 512 ft²; Average depth = 5.75 ft; Pool volume = 22,023 US gal; Weight of water = 91.9 US ton; Cost to fill = $110.11; Time to fill = 36.7 h.
Frequently asked questions
How many gallons is a 16 × 32 pool?
With 3½ ft to 8 ft depth (average 5.75 ft): 512 ft² × 5.75 × 7.48 ≈ 22,000 gallons.
How long does it take to fill a pool?
At 10 gpm from a garden hose, about 36 hours for 22,000 gallons.
Why do I need the pool volume?
Chemical doses, heater sizing and pump turnover are all based on gallons.
What formula does the Pool Calculator use?
Average depth = (shallow + deep) ÷ 2.