Pool Volume Calculator (Litres) + Chlorine & Salt Dose Calculator
Measure your pool in metres, get the volume in litres, then work out a chlorine or salt dose. It's simple arithmetic, so the product label always has the final say.
Knowing how many litres your pool holds is the starting point for every chemical dose, every pump-running decision and every robot cleaner spec. This calculator does three jobs:
- Works out your pool volume in litres from measurements in metres.
- Estimates how much chlorine raises your free chlorine to a target level.
- Estimates how much salt a salt-chlorinated pool needs.
Read this first. These are arithmetic estimates, not instructions. Always read and follow the directions on your chemical's label and your chlorinator's manual. Never mix pool chemicals together, always add chemicals to water (never water to chemicals), and keep everyone out of the pool while you're dosing.
The calculator
1. Pool volume
Freeform estimate: longest length × widest width × 0.85. Treat it as a rough figure; your pool builder's plans will be more accurate.
2. Chlorine dose
Dichlor also adds stabiliser (cyanuric acid) every time you use it. NSW Health says stabiliser shouldn't go above 50 mg/L, so test it regularly if you use dichlor or trichlor.
3. Salt (salt-chlorinated pools)
How the maths works
Volume
- Rectangle: length × width × average depth
- Oval: 3.14 × (length ÷ 2) × (width ÷ 2) × average depth
- Round: 3.14 × (diameter ÷ 2)² × average depth
- Average depth: (shallow end + deep end) ÷ 2
That gives cubic metres. One cubic metre is 1,000 litres. An 8 m × 4 m pool that runs from 1.0 m to 1.8 m deep averages 1.4 m, so it holds 8 × 4 × 1.4 = 44.8 m³, or about 44,800 litres.
Chlorine
One part per million (ppm) is the same as 1 milligram per litre. Raising 1,000 litres by 1 ppm takes 1 gram of available chlorine. Products contain different amounts:
| Product | Typical available chlorine | Notes |
|---|---|---|
| Liquid chlorine (sodium hypochlorite) | 12.5% (about 125 g per litre) | Loses strength as it ages, especially in heat. Store it in the shade and buy it fresh. |
| Granular calcium hypochlorite | Check the label (commonly about 65%) | Adds calcium hardness over time. |
| Dichlor (stabilised granular) | 56–62% (NSW Health) | Adds stabiliser with every dose. |
| Trichlor (tablets or sticks) | About 90% (NSW Health) | Slow-dissolving and acidic. Adds stabiliser. Not covered by this calculator. |
The calculator divides the grams of available chlorine you need by the strength of your product. The real dose is usually higher than the theoretical one, because leaves, sunlight and swimmers consume chlorine as you add it. So add it in stages and retest.
What levels to aim for. SA Health recommends free chlorine of 1.0–3.0 mg/L (ideally 2) and pH 7.2–7.6 for home pools, with testing before use and at least daily. NSW Health says outdoor pools using stabiliser need at least 3 mg/L free chlorine, with stabiliser kept around 30 mg/L and no higher than 50 mg/L.
Shock dosing after storms or heavy use
SA Health's guidance for shock dosing is to reach 10 mg/L free chlorine and hold it for at least an hour with the pump running. Their example is 200 mL of 12.5% liquid chlorine, or 30 g of granular calcium hypochlorite, per 1,000 litres. That's more than the raw arithmetic suggests, because a dirty pool uses up chlorine quickly. Don't swim until free chlorine is back down to 4 mg/L, which may mean waiting overnight.
Got a robot cleaner? Take it out of the pool before you shock dose. Zodiac's Alpha iQ manual says not to use the cleaner during shock chlorination. Beatbot's AquaSense 2 Pro manual lists a maximum of 4 ppm chlorine and 5,000 ppm salt for the robot. Check your own model's manual for its limits.
Salt
Salt is measured in ppm too, but the numbers are much bigger. 1,000 ppm = 1 kg of salt per 1,000 litres. Raising a 44,800 L pool by 1,000 ppm therefore takes about 45 kg, a bit over two 20 kg bags.
The right salt level depends on your chlorinator, and mineral and low-salt systems differ a lot. Use the figure in your chlorinator's manual, not a general rule of thumb. Salt only leaves the pool through splash-out, backwashing and rain overflow. If you overshoot, the only fix is to partly drain and refill, so go slowly.
Measuring tips
- Measure the water surface, not the coping, for length and width.
- For pools with a long gradual slope, take depth readings at several points and average them.
- Spas joined to the pool share its water. Calculate the spa as a separate small rectangle or circle and add it on.
- Write your volume on the inside of the filter cover or the chemical cupboard door so you never have to work it out again.
Next: if you're thinking of automating the cleaning, see our cordless vs corded robot cleaner guide. If summer's coming, work through the Brisbane and Queensland summer pool checklist.
Sources: SA Health – Pools at home and maintaining them · NSW Health – Stabiliser (cyanurate) use in outdoor swimming pools · NSW Health – Healthy swimming pools · Zodiac Alpha iQ owner's manual · Beatbot AquaSense 2 Pro user manual.
Save this guide for later
Pin it to your pool board so it's there when you need it.
Save to Pinterest More pool ideas on Pinterest →Frequently asked questions
How do I calculate how many litres are in my pool?
Multiply length × width × average depth (all in metres) to get cubic metres, then multiply by 1,000 for litres. Average depth is the shallow-end depth plus the deep-end depth, divided by two. For a round pool use 3.14 × radius × radius × average depth.
What chlorine level should a home pool be?
SA Health recommends keeping free chlorine at 1.0–3.0 mg/L (ppm), ideally 2 mg/L, with pH between 7.2 and 7.6. NSW Health advises that outdoor pools using stabiliser (cyanuric acid) need at least 3 mg/L free chlorine.
How much liquid chlorine raises 1 ppm?
In theory, about 80 mL of 12.5% liquid chlorine raises 10,000 litres by 1 ppm (1 L per 125,000 L). Real pools use chlorine up as you add it, so add in stages and retest. Follow the label on your product.
How much salt do I need for a salt water pool?
Each 1,000 ppm of salt needs 1 kg per 1,000 litres. For example, raising a 50,000 L pool from 3,000 to 4,000 ppm takes about 50 kg. The right level depends on your chlorinator, so check its manual.