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 pool gallons
17,280
Average depth
4.50
ft
Total cubic feet
2,304
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter length (ft).
- 2Enter width (ft).
- 3Enter shallow end depth (ft).
- 4Enter deep end depth (ft).
- 5Read your total pool gallons on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Every pool chemical — chlorine, algaecide, pH adjuster, shock — is dosed against total pool volume in gallons, so getting an accurate gallon count is the foundation of correct water balancing. A rectangular pool's volume is straightforward: length times width times average depth times a conversion constant of 7.5 gallons per cubic foot, since that's how many gallons fit in one cubic foot of water. Average depth matters because most residential pools slope from a shallow end to a deep end rather than holding one constant depth, so using the average of the two rather than either extreme gives a far more accurate total than assuming a flat depth throughout. This calculator takes length, width, shallow depth, and deep depth, averages the two depths, and multiplies out to total gallons. Under-dosing chemicals because your gallon estimate was too low leaves a pool vulnerable to algae and bacteria, while over-dosing wastes product and can irritate skin and eyes, so this conversion is worth getting right before every shock treatment or seasonal opening.
Worked example
Using the values the calculator loads with:
Inputs
- Length: 32 ft
- Width: 16 ft
- Shallow end depth: 3 ft
- Deep end depth: 6 ft
Results
- Total pool gallons: 17,280
- Average depth: 4.5
- Total cubic feet: 2,304
What each field means
Inputs
- Length (ft)
- The length used in the calculation, measured in ft. Starts at 32 ft so you have a working example on load.
- Width (ft)
- The width used in the calculation, measured in ft. Starts at 16 ft so you have a working example on load.
- Shallow end depth (ft)
- The shallow end depth used in the calculation, measured in ft. Starts at 3 ft so you have a working example on load. Accepted range: 1–12 ft.
- Deep end depth (ft)
- The deep end depth used in the calculation, measured in ft. Starts at 6 ft so you have a working example on load. Accepted range: 1–16 ft.
Results
- Total pool gallons
- 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.
- Average depth
- ft
- Total cubic feet
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why multiply by 7.5?
One cubic foot of water holds 7.48 gallons, rounded to 7.5 for practical pool math, so multiplying a pool's cubic footage by 7.5 converts volume directly into gallons.
Why use average depth instead of deep end depth?
Using only the deep end depth overstates volume since most of the pool's shallow-to-deep slope holds less water than the deepest point, so averaging the two gives a far more accurate total.
How accurate does my gallon count need to be for chemicals?
Within 5-10% is fine for most chlorine and shock dosing since product labels already build in some tolerance, but very inaccurate estimates can lead to real under- or over-dosing.
Does a rectangular pool with a shallow shelf change this math?
A tanning shelf or bench reduces total volume slightly; for most residential pools this is a small enough fraction that it can be ignored, but for precise dosing on pools with large shelves, subtract the shelf's estimated volume separately.
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
Round Pool Gallons Calculator
Get total gallons for a round or circular above-ground pool from diameter and depth.
Oval Pool Gallons Calculator
Convert an oval above-ground pool's length, width, and depth into total gallons.
Pool Shock Calculator
Calculate how many bags of pool shock to use based on pool gallons and shock level needed.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Rectangular Pool Gallons Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/pool-gallons-rectangular-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/pool-gallons-rectangular-calculator" target="_blank" rel="noopener">Rectangular Pool Gallons Calculator — RevenueLab</a> (2026).</p>
Source: [Rectangular Pool Gallons Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/pool-gallons-rectangular-calculator) (2026).