Always test your water with a test kit before adding chemicals. Estimates only. Never mix pool chemicals. Per CDC guidelines, verify chlorine is in the safe range before swimming. Verify with your pool professional.

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 chlorine (CDC residential guideline)

Fluid Ounces
—
fl oz of liquid chlorine
Gallons
—
gallons of liquid chlorine
FC Raise
—
ppm

Formula

fl oz = (Target FC − Current FC) × Pool gallons × 0.000128 ÷ Concentration
  • 0.000128 — fl oz of pure 100% chlorine needed to raise 1 ppm in 1 gallon: 1 ppm in 1 gallon = 3.78541 mg chlorine (poolchemcalculators.com), and 1 fl oz of solution ≈ 29,573.5 mg, so the ratio is 3.78541 ÷ 29,573.5 = 0.000128
  • Concentration — product strength fraction (0.10 for 10%, 0.125 for 12.5%, etc.)

Reference: poolchemcalculators.com chlorine calculator — verified June 2026. Per the same source, 0.000128 fl oz of 100% chlorine raises 1 ppm in 1 gallon.

Related calculators: Salt Calculator · Shock Calculator · Alkalinity Calculator · Stabilizer (CYA)

Frequently Asked Questions

What is the target free chlorine level for a pool?

The CDC recommends 1–4 ppm chlorine for residential pools. Salt-water pools should maintain roughly the same free-chlorine target produced by the salt cell — see your chlorinator manual for the exact range.

What is the difference between liquid chlorine and granular chlorine?

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. Per SwimUniversity CYA guidance, if CYA is already at 50+ ppm, use liquid chlorine or unstabilized shock to avoid over-stabilizing.

How does pH affect chlorine effectiveness?

Per poolchemcalculators.com, at pH 7.4 roughly half of chlorine is in the active HOCl form. Keep pH between 7.2 and 7.6 for effective sanitization — test and adjust pH first before adding chlorine.

How often should I test and add chlorine?

Test free chlorine regularly during swim season — more often after heavy use, heat, or rain. Add liquid chlorine or tablets as needed to keep FC in the CDC 1–4 ppm range. High bather load depletes chlorine faster.

Why does liquid chlorine use fluid ounces instead of pounds?

Liquid chlorine is measured by volume (fluid ounces or gallons). The calculator converts the dose to both fl oz and gallons for convenience. Per poolchemcalculators.com, one gallon of 10% liquid chlorine (128 fl oz) raises FC by about 10 ppm in a 10,000-gallon pool.