Pool and hot tub calculators
How many gallons, how much chlorine, acid or salt, and what size pump or heater? Worked out from your pool’s real volume, with the formula shown.
New to pool care? Start here
- How to balance pool water — the order to adjust things in, so pH stops drifting.
- How to shock a pool — how high to take chlorine, and clearing a green pool step by step.
- How to close (winterize) a pool and how to open it in spring.
- Pool words explained — CYA, FC, TA, ppm and the rest, in plain English.
What do you need to work out?
Pick what you’re doing — each one opens its own calculator, then the next steps.
- How many gallons (inground)Gallons or litres in a rectangle, round, oval or kidney pool, with a flat or sloped floor.
- Above-ground poolGallons in a round, oval or rectangular above-ground pool from its size, wall height and how full you fill it.
- Daily chlorineFluid ounces, cups or gallons of liquid chlorine or plain bleach to raise free chlorine by any amount, and how many jugs that is.
- Shocking or a green poolHow much shock — cal-hypo bags, liquid chlorine, bleach or dichlor — to superchlorinate, clear algae (SLAM level) or follow the CDC’s accident response.
- pH or alkalinity too highHow much muriatic acid or dry acid to lower pH or total alkalinity, worked from your test results and pool volume.
- Salt water poolPounds or kilograms of pool salt — and how many 40 lb bags — to bring a salt water pool up to your chlorinator’s target.
- Hot tubHow much dichlor, bleach or liquid chlorine raises a hot tub’s chlorine to target — or how much bromide booster and how many bromine tablets to start a bromine tub.
- Pump & filterThe flow your pump needs to turn the pool over in the hours you choose, checked against your pipe size and filter.
Every calculator, by project
Pool & spa volume 4
Chlorine 6
Water balance 8
Pumps & filters 2
Heating & running costs 5
Filling & water loss 2
Above-ground setup 2
Popular sizes, already worked out
- How many gallons in a 24 ft round pool12,972 gal
- How many gallons in a 16x32 inground pool18,193 gal
- How much liquid chlorine to raise 1 ppm in 10,000 gallons10.2 fl oz (1.3 cups)
- How much chlorine for a 10,000 gallon pool30.7 fl oz (3.8 cups)
- How much liquid chlorine to shock a 10,000 gallon pool92.2 fl oz (2.9 qt)
- How much liquid chlorine to SLAM a pool1.92 gal (7.7 qt)
- How much salt for a 15,000 gallon pool401 lb
- How much muriatic acid to lower pH in a 10,000 gallon pool13.7 fl oz (1.7 cups)
- How much baking soda to raise alkalinity in a 10,000 gallon pool4.2 lb
- How much stabilizer for a 10,000 gallon pool2.5 lb (40.1 oz)
- How many gallons in a 7x7 hot tub334 gal
- How much bleach to put in a hot tub2.6 fl oz
- How much sand a Hayward S244T takes300 lb
- What size pump for a 20,000 gallon pool41.7 gpm (158 L/min)
- How much water to drain to lower CYA50%
- How many chlorine tablets for a 10,000 gallon pool2.6 tablets
Guides
- Ideal pool chemistry levels chartPool and hot tub chemistry levels in one chart: chlorine, pH, alkalinity, calcium, CYA, salt and bromine, with CDC/MAHC limits beside common home targets.
- Pool chemical dose chart per 10,000 gallonsHow much chlorine, acid, soda ash, baking soda, calcium, stabilizer and salt per 10,000 gallons, worked from the chemistry, plus per 10,000 litres.
- Chlorine types compared: liquid, bleach, cal-hypo, dichlor, trichlor and saltLiquid chlorine, bleach, cal-hypo, dichlor, trichlor and salt cells compared: strength, dose per 1 ppm, what each adds to the water, pH effect, storage.
- Above-ground pool sizes and gallons chartGallons for round above-ground pools from 12 to 33 ft and ovals from 12×24 to 21×41, at 48, 52 and 54 in walls, plus why maker tables give other numbers.
- Hot tub sizes and gallons chartHow many gallons is a hot tub? Real models from 6 to 9 ft with seats and gallons from the makers’ spec sheets, plus inflatable tubs and a swim spa.
- Pool filter sand chart by modelHow much sand your pool filter takes: pounds of #20 silica and 50 lb bags for Hayward ProSeries, Pentair Triton II and Sand Dollar, and Intex models.
Frequently asked questions
How do I work out how many gallons are in my pool?
Multiply the surface area (sq ft) by the average depth (ft) and by 7.48, the number of US gallons in a cubic foot. A 16 × 32 ft pool running from 3.5 ft to 6 ft deep averages 4.75 ft: 16 × 32 × 4.75 × 7.48 ≈ 18,193 gallons. Round pools use 3.1416 × radius² for the area. The pool volume calculator handles rectangles, rounds, ovals, kidneys and sloped floors.
How much liquid chlorine raises free chlorine by 1 ppm?
In 10,000 gallons, about 10 fl oz of 12.5% liquid chlorine or 13 fl oz of 10% raises free chlorine by 1 ppm. Weaker household bleach takes more — about 21 fl oz at 6%. The strength is printed on the label and drops as the jug ages, so test after it has circulated. See how much liquid chlorine to raise 1 ppm.
What chemical levels should a pool have?
The CDC recommends free chlorine of at least 1 ppm in pools (2 ppm if you use stabilizer, 3 ppm in hot tubs) and a pH of 7.0–7.8. The Model Aquatic Health Code allows total alkalinity of 60–180 ppm and caps stabilizer (CYA) at 90 ppm. The ideal pool chemistry levels chart lists every level with its source, including the common home-pool targets.
Are the doses exact?
No — they are estimates from the chemistry and the product strength on the label. Real products vary, liquid chlorine loses strength in storage, and test kits have their own error. Add the dose (or a little less for acid), let the pump circulate it, retest, then adjust. Always follow the product label.
Is it safe to mix pool chemicals?
No. Never mix chemicals with each other, and never mix chlorine with acid — it releases chlorine gas. Different chlorine types (cal-hypo and trichlor in particular) can react violently. Add each chemical to the pool water separately, with the pump running, and keep separate scoops and buckets.
Do the calculators work in litres and metric?
Yes. Every calculator has a US / metric toggle and converts what you have typed — gallons to litres, ounces to grams, °F to °C. Pool chemistry in ppm is the same in both systems (1 ppm = 1 mg per litre).