To raise free chlorine (FC) by a target amount, dose by volume. Gallons × ppm increase, divided by a product constant, gives the ounces (or fluid ounces) of chlorine to add.
The example
20,000 gal, raise FC 3 ppm.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | 2 × 3 × 10.7 | — |
| 3 | Liquid chlorine | → ~64 fl oz |
The formula
The formula:
How it works
How it works:
- Find the product constant — the dose per 10,000 gal to raise FC by 1 ppm (varies by chlorine type/strength).
- Multiply by volume (in 10,000s) and the ppm increase you want.
- For cal-hypo (granular), use its weight-based constant instead.
- Always test after and adjust — demand and sunlight change the result.
Educational use only — not chemical-safety or professional advice. Pool chemical dosing varies by product strength, water chemistry, and local rules. Always follow the product label, add chemicals to water (never water to chemical), test before and after, and never mix chemicals. Verify with a professional.
Try it: interactive demo
Gallons, ppm increase, dose per 10k (fl oz/ppm).
Variations
In cups
Fl oz ÷ 8:
Granular (cal-hypo)
Weight-based:
Shock to breakpoint
Raise to ~10× CC:
Pitfalls & errors
Product constant. Dose per 10k varies by chlorine type and strength.
Test after. Chlorine demand and sun change the result — retest.
Not advice. Follow the label; never mix chemicals.
Practice workbook
Frequently asked questions
How do I calculate a chlorine dose in Excel?
What's the dose per 10,000 gallons?
Should I retest after dosing?
Stop fighting formulas. Learn them in a day.
This recipe is one of hundreds of real-world formulas we teach. Our Excel Formulas & Functions class covers lookups, logic, text, and dynamic arrays hands-on — live in Dallas–Fort Worth, Houston, Austin, Oklahoma City, Denver, or online.
See the Formulas & Functions Class