Pool Chemical Calculator
Enter your pool's volume to find how much shock to add to raise chlorine, and — for a salt pool — how much salt to reach your target level.
Shock (raise chlorine)
Salt (for saltwater pools)
Keeping a pool balanced comes down to dosing the right amount of chemical for the water's volume. Add too little and algae takes hold; too much wastes product and can irritate swimmers. This calculator handles the two most common jobs: shocking the pool to raise chlorine, and topping up salt in a saltwater system.
How pool dosing is calculated
Chemical doses scale with the number of gallons and how far you want to move a reading. Shock is figured from a standard cal-hypo (73% available chlorine) rate; salt is a direct weight calculation from the ppm change.
Salt (lb) = Gallons × (Target − Current ppm) × 8.34 ÷ 1,000,000
| Reading | Typical target |
|---|---|
| Free chlorine | 1–3 ppm (shock to ~10+) |
| Salt (saltwater pool) | 2,700–3,400 ppm (check your unit) |
| pH | 7.2–7.6 |
Worked example
A 20,000-gallon pool, raising chlorine 10 ppm and bringing salt from 0 to 3,200 ppm:
| Shock = (20,000 ÷ 10,000) × (10 ÷ 7.5) | ≈ 2.7 lb |
| Salt = 20,000 × 3,200 × 8.34 ÷ 1,000,000 | ≈ 534 lb |
Dosing safely
Always run the pump while adding chemicals, and never mix products together in the same container — combining chlorine types can be dangerous. Add salt gradually and give it a day to dissolve before trusting the reading. Shock in the evening so sunlight doesn't burn off the chlorine before it works, and retest the water before anyone swims. When in doubt, follow the label rate on your specific product, which overrides these general figures.