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Pool Volume Calculator | Compute Pool Gallons From Dimensions

Determine your pool's volume in gallons and litres from the length, width and average depth, with the shape-specific formula applied. The gallon figure sizes your pump, filter and chemical doses — enter the pool's dimensions and get the numbers you need.

Last updated: June 2026 · Free · No sign-up required

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Results

Enter values above and click Calculate to see your result instantly.

How the Calculator Pool works

Behind the inputs above sits one rule: Gallons = length × width × average depth (ft) × 7.48. The tool evaluates it instantly with the values you enter.

For context, the sections beneath the calculator include typical values, a worked example you can recompute by hand, and an FAQ covering the practical details of pool volume calculator.

From our guides

Quick reference

Pool typeVolume formula (ft)× gallons
RectangularL × W × avg depth× 7.48
Roundπ × r² × avg depth× 7.48
Ovalπ × (L/2) × (W/2) × depth× 7.48

info Calculator Pool

Free math calculator — enter your numbers and get an instant, accurate result.

info Private by design

Everything runs locally in your browser. No uploads, no accounts, no tracking.

info Works everywhere

Fully responsive and mobile-friendly — calculate on any device, any time.

info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

Avg depth tipUse
Constant depthThat single depth
Shallow + deep end(shallow + deep) / 2
Metric poolsVolume in m³ × 1000 = litres

lightbulb Worked example

Let's say you are using the Calculator Pool. Calculates pool volume using Gallons = length × width × average depth (ft) × 7.48, in real time in your browser. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Gallons = length × width × average depth (ft) × 7.48 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Gallons = length × width × average depth (ft) × 7.48

The Calculator Pool is built on a well-established calculation method. It uses the formula Gallons = length × width × average depth (ft) × 7.48 to turn your inputs into a reliable result. Calculates pool volume using Gallons = length × width × average depth (ft) × 7.48, in real time in your browser. The steps are shown on the page so you can follow the reasoning from input to output.

Pool volume is the water capacity. Find the volume in cubic feet, then convert to gallons (1 ft³ = 7.48 US gallons).

  1. Measure length, width and average depth in feet.
  2. For a sloped floor, average depth = (shallow + deep) / 2.
  3. Multiply length × width × average depth for cubic feet.
  4. Multiply cubic feet by 7.48 for US gallons.

Worked example: A 32 × 16 ft pool averaging 5 ft deep holds 32 × 16 × 5 × 7.48 = 19,149 gallons.

What is the Calculator Pool?

The Calculator Pool is a free, browser-based math calculator tool that helps you Calculates pool volume using Gallons = length × width × average depth (ft) × 7.48, in real time in your browser.. Instead of working through the math by hand or in a spreadsheet, you enter your values and the calculator returns an accurate result instantly — while still showing the formula and the steps so you can verify the reasoning. It is designed for quick everyday use: no sign-up, no installation, and everything runs locally in your browser for complete privacy.

How to use the Calculator Pool

  1. Enter the required values into the input fields.
  2. Press the calculate button — the result appears immediately, updated live as you change any value.
  3. Read the step-by-step breakdown below the result to see exactly how the calculation was performed.
  4. Use the interpretation guide to understand what the result means for your situation, and try different inputs to see how they change the outcome.

How to use the Pool Calculator

Enter the pool's length, width, and average depth in feet, then choose the shape — rectangular or round — and press calculate. The tool applies Gallons = length × width × average depth (ft) × 7.48 for rectangular pools, where 7.48 is the number of US gallons in a cubic foot. For a 20 × 40 ft pool averaging 6 ft deep, that is 4,800 cu ft × 7.48 ≈ 35,900 gallons. The result also shows litres and surface area.

Interpreting your result

The gallon volume is the master number for pool ownership: it sizes the pump and filter, determines the chemical doses (most treatments are quoted per 10,000 gallons), and estimates fill time and water cost. For irregular pools, measure the average depth as a rough midpoint between shallow and deep ends. The surface area is what determines evaporation and heater sizing. Once you know the volume, a 10,000-gallon-per-24h filter cycle, 1–3 ppm chlorine targets, and similar maintenance numbers all become computable.

Common mistakes to avoid

The most common error is using the maximum depth instead of the average — a pool with 3 ft and 9 ft ends averages 6 ft, and using 9 doubles the estimate. Second, mixing units: the formula needs feet and produces US gallons; a metre-based measurement needs conversion first. Third, using outside dimensions that include coping and walls — the water volume is based on interior dimensions. Finally, forgetting that rounded and freeform pools need the shape factor; the rectangular formula undercounts them.

Tips for best results

Measure the interior at the waterline, not the deck. For sloped floors, average the shallow and deep depths rather than guessing. Use the volume to calculate chemical doses precisely — most pool chemical labels quote per 10,000 gallons, and the difference between 15,000 and 20,000 gallons changes a dose by 25%. When filling a new pool, multiply the volume by your water rate to estimate cost. Re-measure after any renovation that changes the depth.

Authoritative source: Wolfram MathWorld

Frequently asked questions

How do you calculate pool volume in gallons?
Enter the required values into the input fields and press the calculate button. The tool applies the formula Gallons = length × width × average depth (ft) × 7.48 and returns the result with a short explanation of each step, so you can check the working yourself.
How do I find average depth?
Measure the depth at the shallow end and the deep end, then average them: average depth = (shallow + deep) ÷ 2. A pool that is 3 ft at one end and 9 ft at the other has an average depth of 6 ft. For pools with gradual slopes this approximation is accurate; for sudden drop-offs, divide the pool into sections and average the section volumes.
How many gallons is a 15-foot round pool?
The Calculator Pool is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Calculates pool volume using Gallons = length × width × average depth (ft) × 7.48, in real time in your browser. There is no limit on usage, and it works on any device.
Why multiply by 7.48?
The factor 7.48 converts cubic feet to US gallons: one cubic foot holds exactly 7.48052 gallons. So a pool volume measured in cubic feet (length × width × average depth) becomes gallons by multiplying by 7.48. It is the same conversion used for aquariums and tanks, and it is exact to the standard definition of the gallon.
How do I get litres instead of gallons?
The calculator shows both units: one US gallon equals 3.78541 litres, so multiply the gallon figure by 3.78541 (or use the direct metric path: volume in m³ × 1,000). For a 35,900-gallon pool, that is about 135,900 litres. Litres are the standard for pool chemistry and water bills in most countries outside the US.
What does the Calculator Pool do?
Calculates pool volume using Gallons = length × width × average depth (ft) × 7.48, in real time in your browser. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.
What formula does the Calculator Pool use?
The Calculator Pool uses the standard Gallons = length × width × average depth (ft) × 7.48. You enter your values, and the calculator applies the formula step by step, showing the working so you can verify the math and understand how the result is derived rather than trusting a black box.
Is the Calculator Pool free and private?
Yes — the Calculator Pool. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.
How accurate is the Calculator Pool?
The Calculator Pool applies the standard formula: Gallons = length × width × average depth (ft) × 7.48. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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