Pool Volume & Chemical Calculator
Measure once, dose right. Enter your pool shape and depths to get the water volume in gallons and litres, then enter today's test-strip readings to see exactly how much chlorine, soda ash, muriatic acid, or baking soda it takes to reach your targets.
Pool size
Water test readings
How to use this calculator
1. Measure the water, not the pool
Take your length, width, or diameter at the waterline rather than across the coping or the deck. A round above-ground pool is measured wall to wall through the middle; an oval needs the long axis and the short axis; a kidney or freeform shape uses its longest length and its widest width, and the calculator applies the standard 0.85 freeform factor.
2. Get the average depth right
This is the number most people fumble. Enter the shallow-end depth and the deep-end depth and the calculator averages them. A 3 ft to 8 ft pool averages 5.5 ft, not 8 ft — using the deep end alone would overstate your volume by nearly half and send every chemical dose the same distance wrong.
3. Enter today's readings, then dose in order
Type in the free chlorine, pH, and total alkalinity from a fresh test strip or drop kit alongside the targets you want. The dosing plan lists the chemicals in the order to add them: alkalinity, then pH, then chlorine. Work down the list with a circulation break between each one.
Tips for a sharper result
Write your gallonage on the inside of the pump lid once you have it — you will use it every week for years. Start with about three quarters of any calculated dose, circulate, and retest: it is trivial to add more chlorine and slow work to pull it back out. And test in the afternoon rather than first thing, when a full day of sun has already taken its bite out of the chlorine.
Pool volume and chemistry FAQs
How do I calculate my pool volume in gallons?
Find the water surface area in square feet, multiply by the average depth in feet to get cubic feet, then multiply by 7.48 because one cubic foot holds about 7.48 US gallons. A rectangle uses length × width; a round pool uses π × radius²; an oval uses π × half the long axis × half the short axis; a kidney or freeform pool is close enough at 0.85 × length × width. Average depth is the shallow depth plus the deep depth, divided by two.
What are the ideal chlorine, pH, and alkalinity levels?
Free chlorine of 1–3 ppm, pH between 7.4 and 7.6, and total alkalinity between 80 and 120 ppm are the usual targets for a residential pool. pH under 7.2 is corrosive to metal fittings and plaster; pH over 7.8 makes chlorine sluggish and clouds the water. Alkalinity is the buffer that keeps pH from swinging, which is why it is the reading to fix first.
How much cal hypo or liquid chlorine raises free chlorine by 1 ppm?
About 2 oz of 65% calcium hypochlorite per 10,000 gallons raises free chlorine roughly 1 ppm. Liquid chlorine at 12.5% sodium hypochlorite takes about 10 fl oz per 10,000 gallons for the same 1 ppm. Pick one product, not both. Cal hypo also drives calcium hardness up over the seasons, while liquid chlorine adds a little salt and loses strength sitting in the shed.
Should I adjust alkalinity or pH first?
Alkalinity first. Total alkalinity buffers pH, so correcting it usually drags pH most of the way to target on its own and shrinks the pH dose you still need. Add sodium bicarbonate to raise alkalinity, circulate for several hours, retest, and only then decide whether pH needs soda ash or muriatic acid. Watch out for the overlap: muriatic acid lowers pH and alkalinity together, so a single dose can overshoot both.
How accurate are these chemical doses?
They are planning estimates built from the standard per-10,000-gallon rules of thumb, and the dosing plan prints every rule it used so you can check the arithmetic. Real demand shifts with water temperature, cyanuric acid level, calcium hardness, bather load, and how strong your chlorine actually still is. Add roughly three quarters of the figure, circulate, retest, and top up.