01
The purpose
What does this calculator estimate?
Find the exact amount of chlorine to raise your free chlorine to target — for liquid, cal-hypo, dichlor, and trichlor.
Water Chemistry · B1
Pool Chlorine Dosage Calculator
Find the exact amount of chlorine to raise your free chlorine to target — for liquid, cal-hypo, dichlor, and trichlor.
Measure the inputsAdd liquid chlorine in the evening — sunlight burns off unstabilized chlorine fast during the day.
Read the full resultTrichlor and dichlor also raise CYA; rely on them all summer and your stabilizer creeps too high.
Check the boundaryPour liquid chlorine slowly in front of a return jet with the pump running to spread it evenly.
Useful forWater ChemistryPlanningComparisonVerification
Live calculation
Chlorine dose
✓ Checked May 2026
Enter your volume, current and target free chlorine, and product type.
Recommended dose
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Enter pool volume and current and target free chlorine to calculate the dose.
Enter the known values. Let the engine handle the calculation.
✓ Formula checked↻ Live result○ No account needed
Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.
The result, explained
Use the Pool Chlorine Dosage Calculator result with context.
Find the exact amount of chlorine to raise your free chlorine to target — for liquid, cal-hypo, dichlor, and trichlor.
02
The tool
What information does it use?
- Pool volume: Don't know it? Use our volume calculators first.
- Current free chlorine (FC): From your test kit, in ppm.
- Target free chlorine (FC): Most pools target 2–4 ppm.
- Chlorine product: Pick the exact product you'll use — strength changes the dose.
03
The method
How to use this calculator
- Pool volumeDon't know it? Use our volume calculators first.
- Current free chlorine (FC)From your test kit, in ppm.
- Target free chlorine (FC)Most pools target 2–4 ppm.
- Chlorine productPick the exact product you'll use — strength changes the dose.
04
The relationship
The formula in plain English
Dose = (Volume ÷ 10,000) × (Target FC − Current FC) × product constant
Each product has its own constant (oz per 10k gal per 1 ppm). Cal-hypo 65% = 2.0 oz; liquid 12.5% = 13 fl oz.05
Worked through
A worked example: 20,000 gal pool, FC 1.0 → 3.0 ppm with cal-hypo 65%
- Target increase = 3.0 − 1.0 = 2.0 ppm
- Dose = (20,000 ÷ 10,000) × 2.0 × 2.0 oz = 8.0 oz
- 8 oz cal-hypo dissolved and added in front of a return jet
| Pool volume | Cal-hypo 65% | Liquid 12.5% | Trichlor 99% | Approx. cost* |
|---|---|---|---|---|
| 5,000 gal | 2.0 oz | 6.5 fl oz | 1.4 oz | ~$0.40 |
| 10,000 gal | 4.0 oz | 13 fl oz | 2.7 oz | ~$0.80 |
| 15,000 gal | 6.0 oz | 20 fl oz | 4.1 oz | ~$1.20 |
| 20,000 gal | 8.0 oz | 26 fl oz | 5.4 oz | ~$1.60 |
| 25,000 gal | 10.0 oz | 33 fl oz | 6.8 oz | ~$2.00 |
| 30,000 gal | 12.0 oz | 39 fl oz | 8.1 oz | ~$2.40 |
06
Why it matters
How the result supports the next decision
Add liquid chlorine in the evening — sunlight burns off unstabilized chlorine fast during the day.
Trichlor and dichlor also raise CYA; rely on them all summer and your stabilizer creeps too high.
07
Good inputs
Improve the estimate before relying on it
- Add liquid chlorine in the evening — sunlight burns off unstabilized chlorine fast during the day.
- Trichlor and dichlor also raise CYA; rely on them all summer and your stabilizer creeps too high.
- Pour liquid chlorine slowly in front of a return jet with the pump running to spread it evenly.
- Cal-hypo adds calcium hardness over time — watch CH in plaster pools that use it heavily.
- Re-test 30 minutes after dosing, not immediately, to let the chlorine mix through the full volume.
08
The boundary
How to interpret the result
Follow the product label, add chemicals separately and retest before another dose.
The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.
09
Before acting
What should override this estimate?
- Measured site conditions and current test results
- Product labels and manufacturer specifications
- Qualified-professional advice and applicable local codes
10
Common questions
Frequently asked questions
How much chlorine do I add to raise FC by 1 ppm?
It depends on the product and your pool size. Per 10,000 gallons, raising FC by 1 ppm takes about 2 oz of cal-hypo 65%, 13 fl oz of 12.5% liquid chlorine, or 1.35 oz of trichlor. The calculator scales these to your exact volume and target.
Which chlorine type should I use?
Liquid chlorine and cal-hypo are best for regular dosing because they don't add stabilizer. Trichlor tablets are convenient but add CYA, and dichlor adds CYA too. Use stabilized products early in the season, then switch to liquid or cal-hypo once CYA is in range.
Why does my chlorine disappear so fast?
Three common causes: low cyanuric acid letting UV destroy chlorine, a high chlorine demand from algae or organics, or simply hot sunny weather. If chlorine vanishes within hours, check CYA first, then look for an organic load.
Can I add too much chlorine?
Yes. Very high FC can bleach liners, corrode metal, and irritate swimmers. Don't swim until FC drops below about 5 ppm (or below the shock level relative to your CYA). The calculator targets a normal range so you don't overshoot.
Does chlorine dose change with cyanuric acid level?
The dose to raise FC is the same, but the FC you need to hold rises with CYA. Higher CYA means you must maintain a higher minimum FC for the chlorine to stay effective — roughly 7.5% of your CYA level as a floor.
How much liquid chlorine for a 15,000 gallon pool?
To raise FC by 2 ppm in 15,000 gallons, add about 39 fl oz (just over a quart) of 12.5% liquid chlorine.
How much cal-hypo to raise chlorine 5 ppm?
In 15,000 gallons, raising FC by 5 ppm takes about 15 oz of cal-hypo 65% — just under a pound.
When is the best time to add chlorine?
At dusk or after dark. Adding chlorine in the evening lets it work overnight without UV burning it off, which is especially important if your CYA is low.
Primary sources
Use the result with current guidance.
These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.