Pool Volume & Chemistry Calculator

CHEMISTRY CHLORINE HOME POOL
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By Checked against sources by , Founder & Architect, RECATOOLS Published Updated Last reviewed

Compute pool volume by shape (rectangle, round, oval or oblong) plus chlorine, pH and total alkalinity doses, worked from the chemistry and checked against Taylor Technologies' treatment tables.

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Pool Volume & Chemistry Calculator

Step 1: Pool dimensions
US Gallons
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primary unit
Liters
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metric
Cubic Meters
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m³
Cubic Feet
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ft³
Step 2: Current water chemistry (from test kit)

Free Chlorine (FC)

Range: 1 – 3 ppm (WHO; NEA Singapore)

pH

Range: 7.2 – 7.8 (WHO; NEA Singapore; Taylor)

Total Alkalinity (TA)

Range: 80 – 120 ppm (Taylor)
Recommended dosing

To raise Free Chlorine

Liquid chlorine
—
Cal-hypo (65%)
—
Trichlor tablets (90%)
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To adjust pH

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To adjust Total Alkalinity

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Enter pool dimensions first to enable chemistry dosing
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How to use the Pool Volume & Chemistry Calculator

Measure your pool

For a rectangle, enter length, width and average depth; for a floor that slopes evenly, the average depth is the shallow end plus the deep end, divided by two. For a round pool, enter the diameter. "Oval" pools come in two shapes, and they hold different amounts: a true ellipse, and the oblong most above-ground "oval" pools are, with straight sides and round ends. A 30 × 15 ft oblong holds about 14% more water than an ellipse of the same length and width, so pick the one that matches yours.

Test your current chemistry

Test free chlorine, pH and total alkalinity, and enter the current readings; the calculator works out how much of each chemical moves the water to your target. A drop-titration kit reads more precisely than strips. The targets default to 2 ppm chlorine, pH 7.4 and 100 ppm alkalinity, inside the ranges WHO, Singapore's NEA and Taylor's test-kit chart give. If your kit has an acid/base demand test, enter the drops and the pH dose comes from Taylor's table instead of from the estimate.

Read the dosing recommendations

For chlorine there are three options. Liquid chlorine is dosed by its strength, which you can change: pool chlorine is often 10–12.5%, household bleach weaker. Cal-hypo adds calcium as well as chlorine; trichlor adds cyanuric acid, the stabiliser. For pH, soda ash raises it and muriatic acid lowers it. For alkalinity, baking soda raises it; lowering it takes acid, which also lowers pH.

Adjust carefully — ALK first, then pH, then chlorine

If several readings are off, bring total alkalinity into range first — Taylor's chart says so, because alkalinity is the buffer that decides how far a dose moves pH. Then pH, because pH decides how much of the chlorine is in its active form. Then chlorine. Dilute each chemical in a bucket of pool water before adding it, always acid into water, never water into acid, and never put chlorine and acid in the same bucket. Let the water circulate and retest before adding more.

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Pool chemistry — the three numbers that matter most

Pool water chemistry balances disinfection against bather comfort and the life of the equipment. Free chlorine, pH and total alkalinity matter most, and they interact: alkalinity decides how far a dose moves pH, and pH decides how well the chlorine works. This calculator does the dosing arithmetic; regular testing is what keeps the water in range. WHO's advice for home pools is to measure pH before the pool is used.

The interaction effects that catch beginners

High pH weakens chlorine. Free chlorine is a mix of hypochlorous acid, the strong disinfectant, and hypochlorite ion, a much weaker one, and pH sets the split: WHO's guidelines put hypochlorous acid at 21% of free chlorine at pH 8.0 and 12% at pH 8.5, which is why they keep chlorinated pools at pH 7.2–7.8. Alkalinity sets how hard pH is to move. In the calculator's estimate, taking pH from 7.6 to 7.4 in 10,000 US gallons at 100 ppm alkalinity takes about 8 fl oz of 31.45% muriatic acid, and the same step at 150 ppm takes half as much again. That is why the page no longer uses a fixed dose per 0.2 of pH, and why the order is alkalinity first, then pH, then chlorine.

Alkalinity first, pH second, chlorine third: each one sets how the next behaves.

Where the doses come from

One part per million is one milligram per litre, so raising free chlorine by 1 ppm in 10,000 US gallons takes 37.9 g of available chlorine, whatever product carries it. Divide by the product's strength and you have the dose: 12.8 fl oz of 10% liquid, 2.05 oz of 65% cal-hypo or 1.48 oz of 90% trichlor, exactly the figures in Taylor Technologies' treatment table. Alkalinity works the same way in milliequivalents: 10 ppm in 10,000 gallons is 1.40 lb of baking soda, again Taylor's figure; the page used 21 oz, about 6% short. Cal-hypo adds calcium as it doses, and trichlor adds cyanuric acid, which builds up because it is not used up: Taylor's chart puts the ideal at 30–50 ppm, and the way down is to drain part of the water or switch to unstabilised chlorine for a time.

The ASEAN pool-chemistry angle

Pool chemistry across ASEAN runs under conditions that change the playbook. Tropical sun breaks chlorine down quickly, which is why outdoor pools in the region are usually stabilised with cyanuric acid (CYA), and why trichlor tablets, which add CYA as they dissolve, are common. Stabilised water needs more free chlorine to do the same job: CDC staff, writing in 2021, described the 2018 US Model Aquatic Health Code as requiring at least 2 ppm of chlorine when cyanuric acid is used and keeping cyanuric acid at or below 90 ppm. Warm water all year favours algae, so the 2–3 ppm end of this calculator's target range is the safer place to sit. Heavy rain dilutes chemistry and washes in organic matter, so test after a downpour rather than waiting for the next scheduled test. In Singapore, the National Environment Agency's Guidelines for Managing Aquatic Facilities require licensed pools to test pH and residual chlorine on site at least once a day, and after a faecal or vomit incident a pool reopens only once residual chlorine is back between 1 and 3 ppm and pH between 7.2 and 7.8. Using household bleach: set the liquid strength to the figure on the label. Use only a plain bleach that states its sodium hypochlorite strength; a 5% bleach needs 2.5 times the volume of 12.5% pool chlorine. Cal-hypo and trichlor are sold through hardware stores and pool-supply shops. For testing, a drop-titration kit reads more precisely than strips, which are fine for quick routine checks.

Chloramines, why pH governs chlorine, and the order to dose in

01

The "chlorine smell" is mostly chloramines, made when chlorine reacts with what swimmers bring in. WHO warns that dosing too little chlorine makes the chloramine problem worse, and that combined chlorine should be no more than half the free chlorine, ideally under 0.2 mg/l.

02

pH determines how much chlorine is working. WHO puts the strong disinfectant, hypochlorous acid, at only 21% of free chlorine at pH 8.0 and 12% at pH 8.5.

03

Alkalinity before pH: Taylor's test-kit chart says to bring total alkalinity into range before adjusting pH, because alkalinity buffers pH.

04

Stabiliser has a price. Cyanuric acid binds chlorine and slows its loss to sunlight; WHO caps it at 100 mg/l, and CDC staff reported in 2021 that the Council for the Model Aquatic Health Code had approved a change treating more than 45 ppm of cyanuric acid per 1 ppm of free chlorine as a reason for immediate correction or closure.

05

Never let chlorine and acid meet outside the pool. WHO warns that hypochlorite and acid dosed together form chlorine gas, which may be dangerous to anyone nearby.

06

Taylor Technologies' treatment table puts a 1 ppm chlorine rise in 10,000 US gallons at 12.8 fl oz of 10% liquid chlorine, 2.05 oz of 65% cal-hypo or 1.48 oz of 90% trichlor; this calculator reproduces all three from the chemistry, and gives 10.2 fl oz at 12.5%.

07

1 ppm means 1 part per million — or 1 gram per 1,000 liters. For a 50,000-liter pool, raising free chlorine by 1 ppm means adding 50 grams of pure chlorine.

08

Saltwater pools are NOT chlorine-free. They generate chlorine in-situ via electrolysis (salt + electricity → chlorine + sodium hydroxide). The water still tests as chlorinated.

09

WHO's guidelines put routine disinfection at 1 mg/l of free chlorine throughout the pool, with no more than 3 mg/l in public and semi-public pools and pH 7.2–7.8. The calculator flags targets outside those figures.

10

Singapore's National Environment Agency requires licensed aquatic facilities to test pH and residual chlorine on site at least once a day and keep the records for 12 months. After topping up with fresh water at home, retest too: dilution moves all three key numbers.

📅 Research current as of 16 Oct 2026 · Sources: WHO Guidelines for Safe Recreational Water Environments Vol. 2 (2006): free chlorine 1 mg/l routine, ≤ 3 mg/l public pools, pH 7.2–7.8, cyanuric acid ≤ 100 mg/l; NEA Singapore, Guidelines for Managing Aquatic Facilities (1–3 ppm, pH 7.2–7.8); Taylor Technologies K-1005 treatment tables (per 10,000 gal); NIST Handbook 44 Appendix C (1 US gal = 3.785411784 L); USGS PHREEQC carbonate constants
Standards, published formulas, and reference data are revised over time — check against a current authoritative source before relying on these figures.

Frequently Asked Questions

  • 1) Total alkalinity (80–120 ppm on Taylor's chart) — it is the buffer that decides how far a pH dose moves pH, so Taylor says to bring it into range first. Let the water circulate and retest. 2) pH (7.2–7.8, WHO and NEA). 3) Free chlorine (1–3 ppm, WHO and NEA) — pH decides how much of it is in its active form, so set pH before judging the chlorine reading.

  • What you smell is mostly chloramines, made when chlorine reacts with sweat, urine and other matter swimmers bring in, and WHO notes that adding too little chlorine makes the problem worse. Test total chlorine as well as free: the difference is combined chlorine, which WHO says should be no more than half the free chlorine and ideally under 0.2 mg/l. Taylor's instruction for clearing it is to superchlorinate to breakpoint, at a dose of 10 times the combined chlorine, and to stay out of the water until free chlorine is back below 5 ppm.

  • It depends on what else you want in the water. Liquid chlorine (sodium hypochlorite) adds chlorine and a little salt; dose it by the strength on the container. Cal-hypo (65% on Taylor's chart) adds calcium with every dose. Trichlor tablets (90%) dissolve slowly in a floater or feeder and add cyanuric acid, the stabiliser, which accumulates; Taylor's ideal is 30–50 ppm, and the way down is partial draining and refilling or a spell on unstabilised chlorine.

  • Cyanuric acid (CYA) is a chlorine stabiliser: it binds chlorine and slows its loss to sunlight, which matters in an outdoor pool. Taylor's chart gives 30–50 ppm as ideal and WHO caps it at 100 mg/l. It is not free protection, because bound chlorine is slower to disinfect: CDC staff, writing in 2021, described the 2018 US Model Aquatic Health Code as requiring at least 2 ppm of chlorine when CYA is used, and reported a change approved by the code's council that treats more than 45 ppm of CYA per 1 ppm of free chlorine as needing immediate correction or closure. Indoor pools have no sunlight to protect against. Trichlor tablets add CYA as they dose; liquid chlorine and cal-hypo add none.

  • The chlorine and alkalinity doses are arithmetic on the product's strength and reproduce Taylor Technologies' treatment tables: 12.8 fl oz of 10% liquid, 2.05 oz of 65% cal-hypo and 1.48 oz of 90% trichlor per 1 ppm in 10,000 gallons, and 1.40 lb of baking soda per 10 ppm of alkalinity. They are only as good as the strength you enter. The pH dose is an estimate: it models the carbonate buffer from your alkalinity reading, and leaves out cyanuric acid and borates, which buffer too, so with stabiliser in the water the real dose is larger. If your kit has an acid/base demand test, enter the drops; the dose then comes from Taylor's table, which measures the buffering instead of modelling it. Either way, add part, let it circulate, and retest.

  • (1) Read the label's precautions and wear eye protection and chemical-resistant gloves. (2) Fill a bucket with pool water first. (3) Pour the acid slowly into the water, never water into acid. (4) Pour the diluted mixture slowly into the pool with the pump running. (5) Never put acid and a chlorine product in the same bucket or add them together: WHO warns that hypochlorite and acid together form chlorine gas. Add them separately, with the water circulating in between, and retest pH once the water has mixed.

  • Rain brings in organic matter — dust, leaves, pollen — that uses up chlorine, and an overflowing pool loses chemicals with the water it sheds. Rain also dilutes: alkalinity, cyanuric acid and chlorine fall in proportion to the water added. After a heavy downpour, test rather than waiting for the next scheduled check, and dose from the new readings.

  • Saltwater pools generate chlorine via electrolysis (salt cell converts dissolved salt into chlorine + sodium hydroxide). The pool water still tests as chlorinated and follows the same chemistry rules, so the pH and alkalinity targets and the volume calculation are unchanged. The chlorine dosing is replaced by adjusting the salt cell output % (higher = more chlorine produced). Keep the salt level inside the range the salt cell's manufacturer specifies (it is printed in the cell's manual and varies between models), topping up gradually with bagged pool salt. The cell also makes sodium hydroxide, so pH tends to drift up and acid is the usual correction.

  • No. All calculations run entirely in your browser via JavaScript. There's no server roundtrip — open DevTools → Network and confirm zero outbound requests as you change inputs. Pool dimensions and chemistry readings stay on your device. Safe for confidential commercial pool service estimates, residential pool data, or any property information that shouldn't leave your machine. Close the tab and nothing remains.

  • WHO advises home-pool owners to measure pH before the pool is used, and suggests continuous measurement for public pools; Singapore's NEA requires licensed pools to test pH and residual chlorine on site at least once a day. Test free chlorine and pH most often, alkalinity less often, and cyanuric acid and calcium hardness occasionally. After superchlorinating, test free chlorine before anyone swims: Taylor says to wait until it is below 5 ppm. A drop-titration kit reads more precisely than strips.

Method & sources

How it computes

Volume = area × average depth (rectangle L·W, round πD²/4, ellipse πLW/4, oblong (L−W)W + πW²/4), 1 ft = 0.3048 m, 1 US gal = 3.785411784 L. Chlorine: ppm × L ÷ 1000 g available chlorine ÷ product %. Alkalinity: ppm ÷ 50.043 meq as CaCO3 × NaHCO3 84.006 g, or 20° Bé HCl at 10 meq/mL. pH: closed carbonate model (pK1 6.352, pK2 10.329) or Taylor demand drops. PoolChemistryKernel.

What this tool implements

  • Chlorine dose: 1 ppm = 1 mg of available chlorine per litre; liquid strength is trade per cent (g per 100 mL), dry products by % available chlorine. Reproduces Taylor K-1005: per 1 ppm in 10,000 US gal, 12.8 fl oz of 10% liquid, 2.05 oz of 65% cal-hypo, 1.48 oz of 90% trichlor; 30 ppm superchlorination 3.00 gal of 10%.
  • Alkalinity: mg/L as CaCO3 at 50.043 mg per meq (CIAAW atomic weights); +10 ppm in 10,000 gal = 1.40 lb sodium bicarbonate, −10 ppm = 1.60 pt of 20° Baumé muriatic acid (10.0 meq/mL), both Taylor's table values.
  • pH: an estimate from a closed carbonate system at 25 °C, pK1 = 16.681 − 10.329 = 6.352 and pK2 = 10.329 from USGS phreeqc.dat; it ignores cyanuric-acid and borate buffering and CO2 loss, so with stabiliser the real dose is larger, and the page says so. With Taylor acid/base demand drops it uses Taylor's per-drop doses instead (5.13 oz soda ash, 9.16 fl oz muriatic acid per drop per 10,000 gal).
  • Ranges checked: WHO Vol. 2 (2006) — free chlorine 1 mg/l routine, ≤ 3 mg/l in public and semi-public pools, pH 7.2–7.8, cyanuric acid ≤ 100 mg/l, combined chlorine ≤ half the free and ideally < 0.2 mg/l, hypochlorite and acid together form chlorine gas; NEA Singapore — 1–3 ppm and pH 7.2–7.8, daily testing; Taylor — TA 80–120, CYA 30–50, re-enter below 5 ppm.
  • Corrected 2026-10-16: pH doses were fixed per 0.2 pH regardless of alkalinity (20 fl oz acid per 10,000 gal, ~2.5× the model at 7.6 → 7.4, 100 ppm); baking soda 21 oz per 10 ppm was 6% short; liquid chlorine fixed at 12.5% (10 fl oz, 2% short), now an input; CDC 2023 MAHC figures (pH 7.0–7.8, 1–10 ppm, CYA ≤ 90) could not be read from the code and were replaced; HOCl "~75% at pH 7.0 / ~25% at 8.0" replaced by WHO's 21% at 8.0; "never exceed 10 ppm" advice replaced by Taylor/WHO's 5 ppm re-entry; blank readings silently defaulted; oblong pools were measured as ellipses (12% low for a 30 × 15 ft pool); rounded gallon and cubic-foot constants.

Sources

What can make this go out of date

  • WHO Vol. 2 (2006) and NEA Singapore's aquatic-facility guidelines (Environmental Public Health (Licensable Aquatic Facilities) Regulations 2021) — recheck if either is revised.
  • Taylor K-1005 treatment tables — the doses are chemistry, but the tests pin them to this table; a reprint with different reagent strengths would need the per-drop figures re-read.
  • The CDC Model Aquatic Health Code itself (cdc.gov) could not be fetched from this environment on 2026-10-16; its cyanuric-acid rules are cited through CDC staff's 2021 column, not the code text.
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