Pool Chlorine Calculator
Calculate how much liquid chlorine (sodium hypochlorite) to add to raise your pool's free chlorine level. Dosing constants verified against poolchemcalculators.com and Indiana State Department of Health guidelines (June 2026).
Chlorine Dose Calculator
Recommended: 1–4 ppm (residential), 1–3 ppm (CDC)
Formula
- 0.000133 — fl oz of pure 100% chlorine needed to raise 1 ppm in 1 gallon (derived from 128 fl oz/gal × 8.345 lb/gal water weight ÷ 1,000,000)
- Concentration — product strength fraction (0.10 for 10%, 0.125 for 12.5%, etc.)
Reference: Indiana State Dept. of Health pool chemistry guide; poolchemcalculators.com — verified June 2026. 1 ppm FC in 10,000 gal requires ~12.8 fl oz of 10% liquid chlorine.
Related calculators: Salt Calculator · Shock Calculator · Alkalinity Calculator · Stabilizer (CYA)
Frequently Asked Questions
The CDC recommends 1–3 ppm free chlorine for public pools. For residential pools, 1–4 ppm is the typical target. Salt-water pools should maintain 1–3 ppm FC produced by the salt cell.
Liquid chlorine (sodium hypochlorite, 10–12.5%) adds no stabilizer (CYA) or calcium. Granular dichlor adds CYA with each dose; trichlor tablets also add CYA. If CYA is already at 50+ ppm, use liquid chlorine or unstabilized shock to avoid over-stabilizing.
At pH 7.4, roughly 50% of chlorine is in the active HOCl form. At pH 8.5, less than 10% is active. Keep pH between 7.2 and 7.6 for effective sanitization — test and adjust pH first before adding chlorine.
Test free chlorine at least twice per week during swim season. Add liquid chlorine or tablets as needed to keep FC in the 1–4 ppm range. High bather load, heat, and rain can deplete chlorine faster.
Liquid chlorine is measured by volume (fluid ounces or gallons). The calculator converts the dose to both fl oz and gallons for convenience. One gallon of 10% liquid chlorine (128 fl oz) raises FC by about 10 ppm in a 10,000-gallon pool.