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Pool Direct Supply · Planning tools
Know your numbers before you buy.
Gallons, surface area, chemical doses and equipment sizes — worked out in seconds, on one page. Then call us and we'll double-check the whole pad for free.
Quick answerRectangular pool, feet. For every other shape use the full calculator below.
0 gallons · 0 sq ft surface
01 · Pool volume
How many gallons is my pool?
Pick the shape, enter your measurements in feet, and we'll give you gallons, surface area and average depth. Every other calculator on this page uses this number.
Constant depth? Enter the same number twice. Average depth = (shallow + deep) ÷ 2.
19,200 Gallons (US)
512Surface area · sq ft
5.0 ftAverage depth
72,700Litres
Formula used
L × W × avg depth × 7.5Shared automatically with the chemical and equipment calculators.
02 · Chemical dosing
How much do I add?
Enter your current test reading and where you want it. We'll tell you how much of each product to add for your pool volume. Always add in stages and re-test.
Free chlorine
Target 1–3 ppm (3–5 ppm with CYA above 50).
—Liquid chlorine 12.5%
—Cal-hypo 65% shock
Shock the pool
Raise free chlorine by 10 ppm to clear algae or after heavy use.
—Cal-hypo 65%
—Liquid chlorine 12.5%
pH & alkalinity
Target pH 7.4–7.6 · Total alkalinity 80–120 ppm.
—Baking soda to raise
—Muriatic acid 31% to lower
Cyanuric acid (stabilizer)
Target 30–50 ppm outdoors · 60–80 for salt pools.
—Granular stabilizer
—Too high? Only water replacement lowers CYA.
Salt (for chlorine generators)
Most cells run at 3,200–3,400 ppm. Check your cell's manual.
—Pool salt to add
—40 lb bags
Calcium hardness
Target 200–400 ppm for plaster · 150–250 for vinyl & fiberglass.
—Calcium chloride 77%
—Dissolve in a bucket before adding.
Doses are industry rules of thumb per 10,000 gallons and assume typical product strengths. Product labels win — check the strength on the bottle, add no more than half a dose at a time, run the pump, and re-test before adding more.
Rather have us do the math?Text or email a photo of your test strip and your gallons. We'll reply with a shopping list.
Send my readings03 · Equipment sizing
What size pump, filter and heater do I need?
Ballpark sizes from your gallons and surface area. Use them to shortlist — then call and we'll confirm against your plumbing, voltage and gas line before you order.
Pump — flow rate
40 GPMGPM needed
34 ftEst. feet of head
Read the pump's curve at this head and pick one that clears your GPM. Above-ground: 1 HP up to 24 ft round, 1.5 HP above.
Shop pumps →Filter — minimum size
192 sq ft Sq ft of cartridge area (1 sq ft per 100 gal, min 100)
Never let the filter's max flow rating fall below your pump's GPM. Oversizing a filter is cheap insurance — longer cleaning intervals, lower pressure.
Shop filters →Gas heater — BTUs
122,880 BTU BTU/hr (round up to the next size)
Surface area × temperature rise × 12. Common sizes: 150k · 200k · 250k · 300k · 400k. Bigger heats faster and costs the same per degree.
Shop gas heaters →Heat pump — BTUs
122,880 BTU BTU/hr (round up)
Surface area × (target water − average air temp) × 12. Heat pumps hold temperature rather than blast it, and a cover lets you size down about 30%.
Shop heat pumps →Sanitizer — size
28,800+ gal Minimum salt-cell rating (1.5× your pool)
Salt: a cell rated for at least 1.5× your pool runs at lower output and lasts longer. AOP: rated flow must match your pump. UV: rated for your full volume.
Shop salt systems →Salt to start up
512 lbs · 13 bags Lbs of salt for a fresh fill to 3,200 ppm
Add the salt before you start the cell, brush it in, and run the pump 24 hours before turning the generator on.
Recommended for your pool
Picked for 19,200 gallons · 40 GPM · 512 sq ft
Updates as you change the numbers above. Every unit below is checked against your flow and size — call before you order and we'll confirm the rest.
AOP system Clear Comfort CCW100 90 GPM AOP Pool Sanitation System — Manifold Install Kit Bundle
$3,770.00
Get the whole pad in one order · $0.00
04 · Cheat sheet
Common pool sizes.
Typical gallons at a 5 ft average depth. Your pool is probably close to one of these.
| Pool | Shape | Surface area | Gallons | Typical pump | Typical gas heater |
|---|---|---|---|---|---|
| 12 × 24 ft | Rectangle | 288 sq ft | 10,800 | 1.5 HP VS | 150k–200k BTU |
| 15 × 30 ft | Rectangle | 450 sq ft | 16,900 | 1.5–2 HP VS | 200k–250k BTU |
| 16 × 32 ft | Rectangle | 512 sq ft | 19,200 | 2 HP VS | 250k BTU |
| 18 × 36 ft | Rectangle | 648 sq ft | 24,300 | 2–2.7 HP VS | 300k BTU |
| 20 × 40 ft | Rectangle | 800 sq ft | 30,000 | 2.7–3 HP VS | 400k BTU |
| 24 ft round | Above ground · 4 ft | 452 sq ft | 13,600 | 1–1.5 HP | Heat pump 85k |
| 16 × 32 ft | Kidney | ~400 sq ft | ~15,000 | 1.5 HP VS | 200k BTU |
05 · Free sizing check
Send us your numbers. We'll send back a parts list.
Every calculator here gets you close. A person who does this all day gets you exact — plumbing size, voltage, gas line, brand compatibility and what actually fits on your pad. Free, no account needed.
Call (817) 587-4397 Mon–Fri 8am–6pm CT
Text a photo (817) 587-4397 Test strip, equipment pad, label
Email hello@pooldirectsupply.com Reply within one business day
06 · Good to know
Pool math, answered.
How accurate is the volume calculator?
Within about 5% for regular shapes if your measurements are good. Free-form pools vary more — split them into two or three simple shapes, calculate each, and add them up. Or send us a photo and rough dimensions and we'll estimate it.
Why does pool volume matter so much?
Every chemical dose, the pump flow rate, the filter size, the salt cell rating and the heater size all come from gallons and surface area. Guess it wrong and you'll over-dose chemicals and under-size equipment.
Should I size my pump by horsepower?
No. Size it by flow rate (GPM) against your turnover and plumbing. A variable-speed pump lets you run low most of the day and only ramp up for cleaning or heating — that's where the energy savings come from.
Gas heater or heat pump?
Gas heats fast and works in any weather — best for spas and pools used on short notice. Heat pumps cost less to run and hold a set temperature, but need air above ~50°F. Many owners in Texas pair a heat pump with a cover.
Can I go bigger than the calculator says?
For filters and heaters, yes — it only helps. For pumps, match the plumbing: too much flow through 1.5″ pipe wastes energy and can damage equipment. Salt cells: bigger is better.
Do you help with sizing if I haven't bought anything?
Yes. The sizing check is free whether you order from us or not. Most people do, because we'll also tell you what fittings, unions and valves the job needs so there's only one delivery.
Free shipping · Authorized dealer · Real people
Right size, first time.
Use the numbers above to shortlist, then let us confirm the pad before you order.
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