Pool Chemical Calculator
Calculate how much chlorine, pH adjuster, or alkalinity increaser to add based on your pool volume and current water chemistry levels.
Swimming pool chemical dosing requires precise calculation based on your pool’s volume. Too little chemical and algae and bacteria thrive. Too much and you’ll irritate swimmers’ eyes and skin, damage equipment, and waste money.
Formula: Pool Volume (gallons) = Length × Width × Average Depth × 7.48 For circular pools: Volume = π × r² × Depth × 7.48 Chemical Amount = (Target Level − Current Level) × Pool Volume × Dose Factor
Target water chemistry ranges:
| Parameter | Ideal Range | Unit |
|---|---|---|
| Free Chlorine | 1.0–3.0 | ppm |
| pH | 7.2–7.8 | — |
| Total Alkalinity | 80–120 | ppm |
| Calcium Hardness | 200–400 | ppm |
| Cyanuric Acid (stabilizer) | 30–50 | ppm |
| Total Dissolved Solids | <2,000 | ppm |
Common dose factors (per 10,000 gallons to raise 1 ppm):
- Liquid chlorine (10% sodium hypochlorite): ~13 oz to raise chlorine 1 ppm
- Granular chlorine (trichlor 90%): ~2 oz to raise 1 ppm
- Baking soda (raise alkalinity): ~1.5 lbs to raise alkalinity 10 ppm
- Soda ash (raise pH): ~6 oz to raise pH by 0.2
- Muriatic acid (lower pH): ~26 oz to lower pH by 0.2
- Calcium chloride (raise hardness): ~2 lbs to raise hardness 10 ppm
Worked example: Rectangular pool: 20 ft × 40 ft × average depth 5 ft Volume = 20 × 40 × 5 × 7.48 = 29,920 gallons ≈ 30,000 gallons
Current chlorine: 0.5 ppm. Target: 2.0 ppm. Need to raise by 1.5 ppm. Using liquid chlorine (13 oz per 10k gallons per ppm): Amount = 1.5 ppm × (30,000 ÷ 10,000) × 13 oz = 1.5 × 3 × 13 = 58.5 oz (~1.8 quarts)
pH reads 7.0 (too low). Target 7.4. Raise by 0.4: Soda ash needed = (0.4 ÷ 0.2) × 6 oz × 3 (for 30k gallons) = 2 × 6 × 3 = 36 oz (2.25 lbs)
Important: Always add chemicals to water (not water to chemicals). Add chemicals with pump running. Test water 4–6 hours after adding chemicals. Never mix chemicals together before adding to pool.