Pool chlorine calculator: how much chlorine to add
Enter the pool’s volume, the chlorine you have and your test result. The calculator gives the amount to add — and what else that product puts in the water.
Enter your measurements
- Free chlorine rise
- 3 ppm
- Label-style rate
- 10.2 fl oz (1.3 cups) per 10,000 gal per 1 ppm
- Salt it leaves behind
- 4.9 ppm
In short: work out how much chlorine the rise takes for your pool’s size, then how much of your product contains that much.
Rise: 4 − 1 = 3 ppm
3 ppm × 37,854 L (10,000 gal) = 113.6 g of chlorine (1 ppm = 1 mg per litre)
113.6 g ÷ 125 g per litre (12.5%) = 0.908 L = 30.7 fl oz (3.8 cups)
- Liquid chlorine labelled 12.5% “by weight” is a little stronger per ounce than 12.5 trade percent (about 14 g of chlorine per 100 ml instead of 12.5), and every jug loses strength as it ages. Either way, retest after it circulates.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How much chlorine for a 10,000 gallon pool | 30.7 fl oz (3.8 cups) |
| How much chlorine for a 15,000 gallon pool | 46.1 fl oz (1.4 qt) |
| How much chlorine for a 20,000 gallon pool | 61.4 fl oz (1.9 qt) |
Same chlorine rise with each product
| Product | Add this much | Stabilizer (CYA) this adds | Calcium hardness this adds |
|---|---|---|---|
| liquid chlorine | 30.7 fl oz (3.8 cups) | 0 ppm | 0 ppm |
| bleach | 64 fl oz (2 qt) | 0 ppm | 0 ppm |
| cal-hypo | 6.2 oz | 0 ppm | 2.1 ppm |
| dichlor | 7.2 oz | 2.7 ppm | 0 ppm |
| trichlor | 4.5 oz | 1.8 ppm | 0 ppm |
Every chlorine product delivers the same thing — free chlorine — and differs only in how strong it is and what else it leaves in the water. The calculator works out how many grams of chlorine your pool needs for the rise you want, then how much of your product contains that much.
How the chlorine calculation works
Pool chemistry is measured in parts per million, and in water 1 ppm is 1 milligram per litre. So raising free chlorine by 1 ppm in 10,000 gallons (37,854 litres) takes 37.9 g of chlorine. Divide that by the product’s strength:
grams of chlorine = ppm rise × pool litres ÷ 1,000 liquid (litres) = grams ÷ (label % × 10) granular (grams) = grams ÷ (available chlorine % ÷ 100) pool litres = gallons × 3.785
Liquid strengths are read as available chlorine per 100 ml (what the bleach industry calls trade percent), so 12.5% means 125 g of chlorine per litre. Granular and tablet labels state “available chlorine” as a percentage of the weight.
Chlorine per 10,000 gallons, per 1 ppm
| Product | Typical strength | Raises 10,000 gal by 1 ppm | Also adds (per 1 ppm FC) |
|---|---|---|---|
| Liquid chlorine | 12.5% | 10.2 fl oz | about 1.65 ppm salt |
| Liquid chlorine | 10% | 12.8 fl oz | about 1.65 ppm salt |
| Household bleach | 6% | 21.3 fl oz | about 1.65 ppm salt |
| Cal-hypo | 65% | 2.1 oz (weight) | about 0.71 ppm calcium hardness |
| Cal-hypo | 73% | 1.8 oz (weight) | about 0.71 ppm calcium hardness |
| Dichlor | 56% | 2.4 oz (weight) | about 0.91 ppm CYA |
| Trichlor | 90% | 1.5 oz (weight) | about 0.61 ppm CYA |
The full chart, including bigger rises and other pool sizes, is in the pool chemical dose chart, and the trade-offs between products are in chlorine types compared.
How much chlorine to aim for
The CDC recommends at least 1 ppm of free chlorine in a pool, or 2 ppm if the pool uses stabilizer (cyanuric acid), and a pH of 7.0–7.8. Stabilizer slows chlorine down, so most home pools with 30–50 ppm of CYA run 3–5 ppm — the chlorine and stabilizer calculator scales the target to your CYA. Above 10 ppm is a shock level; check your product’s label before anyone swims.
Worked examples by pool size
- How much chlorine for a 10,000 gallon pool — every product side by side for the most common label size.
- How much chlorine for a 15,000 gallon pool — and how fast tablets or dichlor build up stabilizer.
- How much chlorine for a 20,000 gallon pool — the weekly liquid chlorine budget for a bigger pool.
What each chlorine adds besides chlorine
- Liquid chlorine and bleach add nothing that builds up except a little salt (about 1.65 ppm per ppm of chlorine). They are alkaline when added, but the pH rise mostly reverses as the chlorine is used.
- Cal-hypo adds calcium — about 0.7 ppm of hardness per ppm of chlorine. Fine for low-calcium water; a problem where the fill water is already hard.
- Dichlor adds stabilizer — about 0.9 ppm of CYA per ppm of chlorine. Good for starting up an unstabilized pool, but daily use pushes CYA up quickly.
- Trichlor adds about 0.6 ppm of CYA per ppm of chlorine and lowers pH and alkalinity. See the chlorine tablet calculator for the weekly build-up.
Adding chlorine
- Test first. Add the dose with the pump running, pouring liquid slowly in front of a return jet (not into the skimmer if a tablet feeder or other chemical is upstream).
- Follow the label for granular products — many say to pre-dissolve in a bucket of pool water, adding the chemical to the water, never the reverse.
- Never mix two types of chlorine, and never let chlorine meet acid. Add them hours apart, in different spots, and keep separate scoops.
- Retest after about 30 minutes of circulation and adjust. Evening doses last longer than midday ones in full sun.
What you’ll need
- Liquid pool chlorine (sodium hypochlorite)Budget price
Adds chlorine without stabilizer or calcium. Strength is printed on the label — commonly 10% or 12.5% — and it weakens with age and heat, so buy it fresh.
See options on Amazon (opens in a new tab) - FAS-DPD drop test kit (chlorine, pH, TA, CH, CYA)Mid-range price
A drop-count kit reads free chlorine to 0.5 ppm (or 0.2 ppm), plus pH, alkalinity, calcium and stabilizer. Every dose on this site starts from a test, so this is the one thing worth buying first.
See options on Amazon (opens in a new tab) - Cal-hypo shock (calcium hypochlorite)Budget price
Granular shock in 1 lb bags, typically 65–73% available chlorine. Adds a little calcium with every dose. Pre-dissolve in a bucket of water if the label says to.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much chlorine do I add to raise free chlorine by 1 ppm?
In 10,000 gallons: about 10.2 fl oz of 12.5% liquid chlorine, 12.8 fl oz of 10%, 21 fl oz of 6% bleach, 2 oz (by weight) of 65% cal-hypo or 2.4 oz of 56% dichlor. Scale by your gallons ÷ 10,000.
Can I use household bleach in my pool?
Yes — plain, unscented bleach is the same chemical as pool liquid chlorine (sodium hypochlorite), just weaker. Avoid scented, splash-less and gel bleaches. See how much bleach for a 10,000 gallon pool.
How much chlorine does a 10,000 gallon pool need per day?
It depends on sun, swimmers and temperature — commonly a few ppm a day in summer. Test daily and add enough to stay above your minimum; how much chlorine for a 10,000 gallon pool has the doses for typical rises.
Which chlorine is best for a pool?
There isn’t one best. Liquid chlorine adds nothing that builds up but is bulky; cal-hypo adds calcium; dichlor and trichlor add stabilizer. Many owners use liquid or a salt generator day to day and keep the stabilized kinds for starting a season.
Why is my chlorine still low after adding the dose?
Old liquid chlorine loses strength, sunlight burns chlorine off fast without stabilizer, and algae or organic debris consume it. If chlorine keeps disappearing overnight, test for algae and consider a shock — see the pool shock calculator.
Related guides
Sources
- CDC Healthy Swimming — Home pool and hot tub water treatment and testing (opens in a new tab) — pH 7.0–7.8; free chlorine at least 1 ppm in pools (2 ppm with cyanuric acid) and 3 ppm in hot tubs; no CYA in hot tubs; test twice a day.
- CDC — Model Aquatic Health Code, 5th edition (2024), code (opens in a new tab) — Free chlorine minimum 1.0 ppm (2.0 with CYA, 3.0 in spas); pH 7.0–7.8; CYA at or below 90 ppm; CYA:FC above 45:1 is an imminent hazard; TA 60–180 ppm; turnover tables.
- OxyChem — Soda Bleach Solutions Handbook (re-hosted copy) (opens in a new tab) — Trade percent = grams per litre of available chlorine ÷ 10; weight % NaOCl ≈ 1.05 × weight % available chlorine; strength and specific gravity table.
- HASA — Hasachlor sodium hypochlorite SDS (2026) (opens in a new tab) — Pool liquid chlorine: sodium hypochlorite 12.5% by weight, about 1.2 g/ml.
- Hill Brothers — Sodium hypochlorite 12.5% specifications (opens in a new tab) — 12.5% by weight = 142 g/L available chlorine (14.2 trade percent), 11.9% available chlorine by weight.
- Pool Essentials chlorinating liquid (retail listing) (opens in a new tab) — A 10% sodium hypochlorite pool chlorine.
- US EPA label 57787-18 — calcium hypochlorite 65% (opens in a new tab) — 65% available chlorine; 2 oz per 10,000 gallons raises chlorine about 1 ppm; superchlorinate with 10 oz per 10,000 gallons.
- US EPA label 1258-161 — HTH calcium hypochlorite 73% (opens in a new tab) — Calcium hypochlorite 73% (70% minimum available chlorine); a 1 lb bag shock-treats 15,000 gallons.
- US EPA reg. 42177-80 — sodium dichlor label (ProPools copy) (opens in a new tab) — Dihydrate, 56% available chlorine; 2–3 oz per 10,000 gallons daily; 1 lb per 10,000 gallons to superchlorinate.
- ICC Building Safety Journal (PHTA Recreational Water Quality Committee) — Trichlor: the dependable pool performer (opens in a new tab) — Trichlor is 90% available chlorine and adds 0.6 ppm cyanuric acid for each ppm of chlorine.
- CDC — Pool chemical injuries press release (2014) (opens in a new tab) — Never mix pool chemicals, especially chlorine products with acid; add chemical to water, never water to chemical.
- CDC — Pool chemical safety: storage poster (opens in a new tab) — Separate acid and chlorine; don’t mix different types of chlorine; keep chemicals cool, dry and in original containers.
- US EPA — Introduction to pesticide labels (opens in a new tab) — Pool sanitizers are registered pesticides; the label is the law.