Pool Volume Calculator - Litres, Gallons and Chemical Dosage
Get your pool volume in every unit that matters, plus pump runtime, filter size, chlorine, pH adjuster, alkalinity and salt for freshwater and saltwater pools. Six pool shapes, variable depth, and no guessing.
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Your Pool Volume
Chemical Dosage Table
| Chemical | Target | Amount to Add |
|---|
Pump, Filter and Turnover
| Parameter | Recommended Value |
|---|
Pick your pool shape, enter the dimensions, and the calculator returns volume in litres, US gallons, UK gallons and cubic metres plus every chemical dose and pump specification you need for a healthy pool.
Typical Pool Sizes and Volumes
Use this quick reference to sanity-check your calculation or plan a new pool build. Volumes assume an average depth of 1.5 m (4.9 ft).
| Pool type | Dimensions (m) | Approx. volume (litres) | Approx. volume (US gal) |
|---|---|---|---|
| Small plunge pool | 3 x 2 x 1.2 | 7,200 | 1,900 |
| Small home pool | 6 x 3 x 1.5 | 27,000 | 7,100 |
| Standard family pool | 8 x 4 x 1.5 | 48,000 | 12,700 |
| Large home pool | 10 x 5 x 1.5 | 75,000 | 19,800 |
| Olympic-size | 50 x 25 x 2 | 2,500,000 | 660,000 |
| Round above-ground | 4.5 m dia x 1.2 | 19,000 | 5,000 |
| Oval above-ground | 7 x 3.5 x 1.2 | 29,400 | 7,800 |
Ideal Pool Water Chemistry Ranges
These are the industry-standard targets that every pool should be kept within. The calculator uses these values when computing chemical doses.
| Parameter | Ideal range | Why it matters |
|---|---|---|
| Free chlorine | 1 - 3 ppm | Kills bacteria and algae |
| pH | 7.2 - 7.6 | Affects chlorine effectiveness |
| Total alkalinity | 80 - 120 ppm | Prevents pH bounce |
| Calcium hardness | 200 - 400 ppm | Prevents corrosion and scaling |
| Cyanuric acid | 30 - 50 ppm | Protects chlorine from UV |
| Salt (saltwater pools) | 2,700 - 3,400 ppm | Feeds the chlorinator |
| TDS | Below 1,500 ppm | Overall water balance |
How the Pool Volume Calculator Works
Every result on this page is derived from the standard swimming pool formulas used by pool builders and service technicians. Here is exactly what happens behind the scenes.
- Shape area is computed from the geometry formula for your selected pool type (rectangle, circle, oval, kidney, L-shape).
- Average depth is derived - for variable-depth pools, the shallow and deep ends are averaged.
- Volume is multiplied by the area and average depth to give cubic metres or cubic feet.
- Unit conversions produce litres, US gallons, UK gallons and cubic feet from the same base volume.
- Chemical doses are scaled to your exact volume using industry dosing rates per 10,000 litres.
- Turnover flow rate is calculated as volume divided by your desired turnover time (typically 8 hours for residential).
- Filter size is derived from the required flow rate using standard filtration velocity guidelines.
Pool Volume Formulas
These are the exact geometric formulas the calculator uses for each pool shape.
- Rectangular = Length x Width x Average depth
- Circular = pi x radius^2 x Average depth
- Oval = pi x (long axis / 2) x (short axis / 2) x Average depth
- Kidney = Length x (wide + narrow) / 2 x Average depth x 0.45
- L-shape = (Long leg L x W) + (Short leg L x W) x Average depth
- Freeform = Average length x Average width x Average depth
- Average depth = (shallow end + deep end) / 2
- Water weight = Volume x 1,000 kg (1 m3 = 1,000 kg)
- Turnover flow rate = Volume (US gal) / turnover hours
Worked example: A rectangular pool 10 m x 5 m with shallow 1 m and deep 2.5 m has average depth 1.75 m. Volume = 10 x 5 x 1.75 = 87.5 m3 = 87,500 litres = 23,100 US gallons. With an 8-hour turnover, the pump must move 2,890 gallons per hour.
Chemical Dosing Guide: What to Add and Why
Here is what each chemical does and the standard dosing rule the calculator uses per 10,000 litres (2,642 US gallons) of water.
- Shock chlorine (cal hypo 65%) - 20 g raises free chlorine by 1 ppm. Use 10x dose for shock treatment.
- Daily chlorine (cal hypo 65%) - 2 g per 1 ppm per 1,000 litres, or add 3 - 5 ppm weekly.
- pH Up (sodium carbonate / soda ash) - 10 g raises pH by 0.1 per 10,000 L.
- pH Down (muriatic acid 31%) - 10 mL lowers pH by 0.1 per 10,000 L.
- Alkalinity Up (sodium bicarbonate) - 15 g raises total alkalinity by 10 ppm per 10,000 L.
- Cyanuric acid (stabilizer) - 40 g raises CYA by 10 ppm per 10,000 L.
- Calcium chloride - 15 g raises calcium hardness by 10 ppm per 10,000 L.
- Salt (for saltwater chlorinator) - 3 kg raises salt by 1,000 ppm per 10,000 L.
Frequently Asked Questions About Pool Volume
How do I calculate the volume of my pool?
Multiply your pool's surface area by the average depth. For a rectangular pool, that is length x width x average depth. For a round pool, use pi x radius squared x depth. The calculator on this page handles every common shape automatically - just pick your pool type and enter the dimensions.
How many litres is a 10 x 5 metre pool?
It depends on depth. A 10 m x 5 m pool with a uniform depth of 1.5 m holds 75,000 litres (19,800 US gallons). With a variable depth of 1 m to 2.5 m (average 1.75 m), it holds 87,500 litres (23,100 US gallons). Use the calculator above for exact figures including litres, gallons and cubic metres.
How many gallons is my pool if it is round?
For a round pool, use the formula pi x radius squared x average depth x 264.172 to get US gallons. A 5 m (16.4 ft) diameter pool with 1.2 m (3.9 ft) depth holds approximately 5,000 US gallons or 18,850 litres. The calculator above handles both above-ground and in-ground round pools.
How long should I run my pool pump each day?
The industry standard is to turn over the full volume of water once every 8 hours for residential pools, or every 4-6 hours for commercial pools. This means your pump should run long enough to filter the entire pool volume. For a 50,000 litre pool with a pump that moves 8,000 litres per hour, run it for about 6.25 hours per day (50,000 / 8,000). The calculator shows your exact runtime.
What size pump do I need for my pool?
Divide your pool volume in gallons by the turnover time in hours to get the required flow rate in gallons per hour (GPH). A 20,000-gallon pool with an 8-hour turnover needs a pump rated for 2,500 GPH. Always choose a pump slightly above the calculated requirement so it runs efficiently and lasts longer.
How much chlorine do I add to my pool?
For daily maintenance, you need enough chlorine to keep free chlorine between 1 and 3 ppm. As a general rule, add 2 to 3 grams of 65% calcium hypochlorite per 1,000 litres of water to raise chlorine by 1 ppm. For shock treatment, use 10x that amount. The calculator above gives exact doses for your pool volume and chlorine product.
What is the ideal pH for pool water?
The ideal pH is between 7.2 and 7.6. Below 7.2 makes water acidic, causing corrosion and eye irritation. Above 7.6 makes chlorine less effective and can cause scaling. Test pH at least twice a week and adjust with soda ash to raise or muriatic acid to lower.
How much salt do I need for a saltwater pool?
Target a salt level of 3,000 ppm (parts per million). To raise salt by 1,000 ppm in 10,000 litres of water, add 3 kg of pool salt. For a 50,000 litre pool starting from zero salt, you would need 15 kg to reach 1,000 ppm, or 45 kg to reach the full 3,000 ppm target. Always add salt slowly and let the pump circulate for 24 hours before testing.
How much does it cost to fill a pool with water?
Water cost varies by region. In most areas, municipal water costs between $1 and $5 per cubic metre (1,000 litres). For a 50,000 litre pool, that is $50 to $250. In areas with tiered water pricing or during drought restrictions, it can cost much more. Use the calculator above to enter your local rate and see an exact fill cost.
How much does pool water weigh?
Water weighs 1,000 kg per cubic metre (or 8.34 pounds per US gallon). A 50,000 litre pool holds 50,000 kg (50 metric tons) of water. This matters if you are planning a rooftop pool, above-ground pool or deck-mounted pool - the structural load must be calculated before construction.
What is the difference between US gallons and UK gallons?
A US gallon is 3.785 litres, while a UK (imperial) gallon is 4.546 litres. This means the same pool has roughly 17% more UK gallons than US gallons. Always check which one your local pool products and test kits use - the calculator above shows both.
How often should I test my pool water?
Test free chlorine and pH twice a week year-round, and daily during heavy use or hot weather. Test total alkalinity and calcium hardness monthly. Test cyanuric acid at the start and midpoint of the swimming season. Saltwater pools should also test salt levels monthly.
Can I use this calculator for a hot tub or spa?
Yes. Choose the round or rectangular shape and enter the depth. For small volumes under 2,000 litres, use the same chemical dosing rule the calculator applies, but round up slightly because small volumes swing quickly. The "therapy / spa / plunge" option under Pool use adjusts the turnaround recommendations.
What is turnover rate and does it really matter?
Turnover rate is how long it takes for the entire pool volume to pass through the filter once. It matters because it determines how long you must run the pump to keep water clear and sanitary. A pool with too slow a turnover will develop algae and cloudy water even if chemicals are balanced. Always aim for at least one full turnover per day, with 8 hours being the sweet spot for most residential pools.
References & Standards
- ANSI/APSP-11 - Standard for Water Quality in Public Pools and Spas
- CDC Model Aquatic Health Code (MAHC) - Water quality and turnover
- PHTA - Pool and Hot Tub Alliance, Service Technician Reference
- NSF/ANSI 50 - Equipment for Swimming Pools, Spas, Hot Tubs and Other Recreational Water Facilities
- BS EN 13451 - Swimming pool equipment
- AS 1926 - Swimming pool safety (Australia)
- NSPI - National Spa and Pool Institute standards