The exact amount to add, for your volume and your chemical.
Quick reference — raise FC by 1 ppm in 10,000 US gal
| Chemical | Amount |
|---|---|
| Liquid chlorine 12.5% | 10 fl oz |
| Cal-hypo 67% | 2.0 oz |
| Dichlor 55% | 2.4 oz |
| Trichlor 90% | 1.5 oz |
In 10,000 US gallons: about 2 oz of 67% cal-hypo, 2.4 oz of dichlor, 1.5 oz of trichlor, or 10 fl oz of 12.5% liquid chlorine. Double the volume or the ppm gap, double the dose.
Most pools target 2–6 ppm (aim ~4). Hot tubs on chlorine run 3–6 ppm. High stabilizer (CYA) means you need the upper end.