Pool Chlorine Calculator
Liquid chlorine dose from volume and ppm raise needed.
What it does
Liquid chlorine dosing is proportional: pool volume times the ppm gap divided by product strength. Stronger jugs dose less volume for the same lift, which is why strength sits in every calculation.
The tool above takes volume, ppm raise, and strength in either system. It returns fluid ounces or liters with jug equivalents and cost.
Free chlorine targets near one to three ppm for pools with stabilizer in range. Sunlight burns unstabilized chlorine fast, so evening dosing holds better than noon pours.
Safety outranks precision here. Goggles and gloves for handling, pump running for mixing, acids and chlorine products stored and added apart, always.
How to use
- Switch the unit system first: imperial for gallons, metric for cubic meters.
- Enter pool volume from the pool volume calculator.
- Test free chlorine and enter the gap to target.
- Pick the exact jug strength and dose with the pump on.
Formula
- volume x ppm
- Total chlorine demand of the water.
- strength x 10,000
- Available chlorine per unit: 10% gives 100,000 ppm.
Old jugs lose strength in heat and sun, so stale chlorine underdoses the math. Buy fresh stock and store cool and dark.
Worked example
Example: 20,000 gal raised 2 ppm with 10% chlorine
Pool 20,000 gallons, gap 2 ppm, 10% liquid chlorine at $6 per gallon.
- Gallons: 20,000 x 2 / (10 x 10,000) = 40,000 / 100,000 = 0.4 gal.
- Ounces: 0.4 x 128 = 51 fl oz.
- Cost: 0.4 x $6 = $2.40.
- Add at dusk with pump running, retest in the morning.
Reference table
| Raise | 10% chlorine | 6% bleach |
|---|---|---|
| 1 ppm | 13 fl oz | 21 fl oz |
| 2 ppm | 26 fl oz | 43 fl oz |
| 5 ppm | 64 fl oz | 107 fl oz |
| 10 ppm shock | 128 fl oz | 213 fl oz |
Limits
- Liquid chlorine only. Tablets and shock differ.
- Assumes labeled strength. Old stock runs weak.
- Demand from algae and sun sits outside the gap.
- Stabilizer levels change chlorine effectiveness.
Common mistakes
- Dosing without testing current level.
- Mixing chlorine with acid products.
- Adding at noon sun and losing half.
- Pouring with the pump off, layering chemical.
- Trusting last year jug strength.
Try it yourself
Quick checks. Answers sit tucked under each question.
10,000 gal up 1 ppm with 12.5%?
10,000 x 1 / 125,000 = 0.08 gal, which is 10 fl oz.
Metric: 75 m3 up 1 ppm at 10%?
75 x 1 / 100 = 0.75 L.
Questions
How much chlorine does my pool need?
Volume times ppm gap divided by strength: 20,000 gal up 2 ppm at 10% needs 51 fl oz.
What free chlorine level is right?
Usually 1 to 3 ppm with stabilizer in range. Follow local codes for public pools.
Can I use household bleach?
Plain unscented bleach works in a pinch at 6%, dosed by the same math. No splashless or scented types.
When should I add chlorine?
Evening with the pump running. Sunlight destroys fresh chlorine fast.
Why did levels crash overnight?
Algae, organics, or sunlight demand. Test, dose, and check stabilizer.
Is it safe to swim after dosing?
After levels settle in range with circulation, per product label times.