Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total water volume
7,614
Total cubic feet
1,018
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter pool diameter (ft).
- 2Enter average depth (ft).
- 3Read your total water volume on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
18-foot round is a popular above-ground pool size. This calculator defaults to that diameter with a 4-foot average depth and returns total gallons, which is the key number for sizing pumps, filters, and chemical dosing on a circular pool.
Worked example
Using the values the calculator loads with:
Inputs
- Pool diameter: 18 ft
- Average depth: 4 ft
Results
- Total water volume: 7,614
- Total cubic feet: 1,018
What each field means
Inputs
- Pool diameter (ft)
- The pool diameter used in the calculation, measured in ft. Starts at 18 ft so you have a working example on load.
- Average depth (ft)
- The average depth used in the calculation, measured in ft. Starts at 4 ft so you have a working example on load. Accepted range: 2–10 ft.
Results
- Total water volume
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total cubic feet
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How many gallons is an 18-foot round pool?
At a 4-foot average depth, about 7,616 gallons — a common figure used to size filter pumps and calculate chlorine dosing.
Does an above-ground pool have a uniform depth?
Most do, unlike in-ground pools with a deep end, so the average depth is usually just the wall height minus a few inches for the waterline.
How often should I test water in a pool this size?
Two to three times per week during swim season is standard for above-ground pools this size, more often after heavy rain or heavy use.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). 18 Ft Round Pool Gallons Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/18-ft-round-pool-gallons-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/18-ft-round-pool-gallons-calculator" target="_blank" rel="noopener">18 Ft Round Pool Gallons Calculator — RevenueLab</a> (2026).</p>
Source: [18 Ft Round Pool Gallons Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/18-ft-round-pool-gallons-calculator) (2026).