Pool Volume Calculator
Enter your pool’s shape and dimensions to estimate its volume in gallons and liters — the starting point for every dosing calculation on this site.
Estimated volume
How the estimate works
A rectangular or square pool’s volume is length × width × average depth × 7.5 (the number of gallons in a cubic foot of water, rounded for convenience). A round pool uses its diameter squared × average depth × 5.9, and an oval pool uses length × width × average depth × 6.7 — both derived the same way but adjusted for how a circle or an oval’s footprint compares to a rectangle of the same outer dimensions.
If your pool has a shallow end and a deep end, average the two depths first. Free-form pools, pools with a tanning ledge, or those with a rounded hopper bottom won’t match these formulas exactly — treat the result as a solid planning estimate, and if you have a fill-meter reading from when the pool was first filled, that measured number is always more precise.
Frequently Asked Questions
Why does pool volume matter so much?
Every chemical dose — chlorine, pH adjusters, alkalinity increaser, salt — is calculated per gallon (or per 10,000 gallons) of water. Get the volume wrong and every dose that follows is wrong too, so it's worth measuring your pool once and writing the number down.
What counts as the 'average depth'?
For a pool with a shallow and deep end, average depth is simply (shallow depth + deep depth) / 2. For a flat-bottom pool, the average depth is just the depth of the water.
How accurate are these formulas?
They're the standard rule-of-thumb multipliers used across the pool industry (7.5 for rectangular pools, 5.9 for round pools from the diameter, and 6.7 for oval pools), and they're accurate for pools with a fairly consistent cross-section. A pool with a rounded hopper bottom, a tanning ledge, or an irregular free-form shape will vary from the estimate — for those, many pool professionals use a fill-meter reading during the first fill as the more precise number.
Why do I need the volume if I already have a salt or chlorine system reading?
A salt cell or chlorinator reads a concentration (parts per million), not a total quantity. To turn 'raise the reading by X ppm' into 'add this many pounds or ounces,' every dosing calculator on this site needs your pool's volume as an input.
Planning estimate only. Actual volume varies with pool shape, slope, and any built-in features (steps, ledges, spas) — use a measured fill-meter reading where precision matters.
Pool safety comes first
- Pool Safely (CPSC): "A fence of at least four feet in height should surround the pool or spa on all sides and should not be climbable for children." Fence all four sides, separating the pool from the house, with self-closing, self-latching gates (CDC).
- Pool Safely: "Always watch children when they’re in or near water, and never leave them unattended." Name one adult as the Water Watcher.
- Drain covers: Pool Safely says "never enter a pool or spa that has a loose, broken or missing drain cover." Powerful drain suction "can even trap an adult". Public pools and spas must meet the Virginia Graeme Baker Pool & Spa Safety Act.
- Pumps, heaters and other pool equipment need GFCI protection, and CPSC says to "Have an electrician who is qualified in pool and spa repairs inspect and upgrade your pool, spa or hot tub".
- CDC: hot tub "Water temperature should not be higher than 104°F (40°C)."