Swimming pools · Use case

Pool volume,
before you dose.

Enter length, width, and average depth. Get the volume in US gallons and liters, plus chlorine dosing references for shock and routine maintenance.

For a pool with shallow and deep ends: use the average of the two depths as your height — e.g. (3 ft + 7 ft) ÷ 2 = 5 ft.

Chemical dosing reference

Chlorine math.

Pool chemistry depends on volume. Once you know how many gallons or liters your pool holds, dosing becomes straightforward. The standard targets:

Free chlorine: 1–3 ppm (parts per million)
pH: 7.2–7.6
Total alkalinity: 80–120 ppm
Calcium hardness: 200–400 ppm
Cyanuric acid (stabilizer): 30–50 ppm

Always follow the product label. Numbers vary by chemical concentration and brand. Test your water before adding chemicals, and re-test after dosing.

Chlorine dosing — quick math

For calcium hypochlorite (cal-hypo, ~65% available chlorine):

+1 ppm in 10,000 gal	~2 oz
+1 ppm in 20,000 gal	~4 oz
Shock (10 ppm) in 10,000 gal	~20 oz
Shock (10 ppm) in 20,000 gal	~40 oz

For liquid chlorine (10–12.5% sodium hypochlorite), about 10 fl oz per 10,000 gal raises free chlorine 1 ppm.

Reference pool sizes

Common pool dimensions.

Pool type	L × W × avg depth	Volume
Small backyard	20 × 10 × 4 ft	5,985 US gal
Standard backyard	30 × 15 × 5 ft	16,830 US gal
Large residential	40 × 20 × 5 ft	29,920 US gal
Lap pool	50 × 8 × 4 ft	11,970 US gal
Olympic (50 m)	50 × 25 × 2 m	2,500,000 L

Common questions.

How do I calculate the volume of a rectangular pool?

Multiply length × width × average depth, then convert to gallons or liters. For pools with a shallow and deep end, use the average of the two depths. A 30 × 15 ft pool with average depth of 5 ft holds 2,250 cubic feet, or about 16,830 US gallons.

How do I find the average depth?

For a constant-depth pool, use that single depth. For a pool with shallow and deep ends, add the two depths and divide by 2. A pool with 3 ft shallow end and 7 ft deep end has an average depth of 5 ft.

How much chlorine for my pool?

Routine maintenance typically targets 1–3 ppm free chlorine. For granular calcium hypochlorite: about 2 oz per 10,000 gallons raises free chlorine by 1 ppm. For a shock treatment, use 3–5× the maintenance dose. Always follow the label directions and test before swimming.

What about irregular or kidney-shaped pools?

This calculator is for rectangular pools. For oval or kidney shapes, the standard formula is length × width × average depth × 0.85 — the 0.85 factor accounts for the curved sides. For freeform shapes, break the pool into rectangular sections and sum.

Pool volume,before you dose.

Chlorine math.

Common pool dimensions.

Common questions.

From the blog.

Pool volume,
before you dose.