# Pool Water Calculator

Pool water calculator for volume in gallons and liters, fill time, fill cost, and monthly evaporation top-up. Works as a swimming pool water calculator for all shapes.

## What this calculates

Planning a new pool, refilling after a drain, or budgeting a monthly water bill? This pool water calculator returns the total pool water volume in gallons and liters, the cost to fill from a municipal supply, how long it'll take from a garden hose, a chemical dosing reference for liquid chlorine, and a typical monthly evaporation top-up. Works for rectangle, round, oval, and kidney shapes. Covers above ground pool water calculator use cases and in-ground pools up to 200,000 gallons.

## Inputs

- **Pool Shape** — options: Rectangle, Round / Circular, Oval, Kidney / Freeform — Pool water calculator oval and rectangle supported.
- **Length (or Diameter)** (ft) — min 1, max 300 — Diameter for round pools.
- **Width** (ft) — min 0, max 200 — Ignored for round pools.
- **Average Depth** (ft) — min 0.5, max 20 — (Shallow + deep) / 2 for sloped pools.
- **Water Rate** ($/1000 gal) — min 0, max 50 — Municipal water rate per 1,000 gallons. US average is $3-5.
- **Garden Hose Flow** (GPM) — min 1, max 60 — A standard garden hose flows 9 GPM. Fire hydrant fills go 50-250 GPM.

## Outputs

- **Pool Water Volume**
- **Pool Water Volume (metric)**
- **Cost to Fill** — formatted as currency — Municipal water cost to fill the pool
- **Fill Time** — formatted as text — Estimated time to fill with a garden hose
- **Chlorine Dose Reference** — formatted as text — How much liquid chlorine to raise free chlorine by 1 ppm
- **Typical Monthly Top-Up** — formatted as text — Evaporation and splash loss per month in summer

## Details

Pool Water Volume Formula

  - Rectangle: Length x Width x Avg Depth x 7.48 = gallons

  - Round: pi x Radius^2 x Avg Depth x 7.48

  - Pool water calculator oval: pi x (Length/2) x (Width/2) x Avg Depth x 7.48

  - Kidney: Length x Width x Avg Depth x 7.0 (irregular bottom coefficient)

Converting: 1 cubic foot = 7.48 US gallons = 28.32 liters. 1 gallon weighs 8.34 lbs.

Swimming Pool Water Calculator Reference Volumes

| Pool Size | Shape | Avg Depth | Volume |
|---|---|---|---|
| 16 x 32 ft | Rectangle | 5 ft | 19,150 gal |
| 18 x 36 ft | Rectangle | 5 ft | 24,250 gal |
| 20 x 40 ft | Rectangle | 5 ft | 29,900 gal |
| 24 ft | Round | 4.3 ft | 14,650 gal |
| 18 ft | Round | 4.3 ft | 8,250 gal |
| 15 x 30 ft | Oval | 4.3 ft | 11,380 gal |
| 12 x 24 ft | Oval | 4 ft | 6,770 gal |
| 16 x 32 ft | Kidney | 5 ft | 17,900 gal |

Above Ground Pool Water Calculator

An above ground pool water calculator uses the same math as an in-ground. Most above ground pools are round or oval with a consistent flat bottom, so the single-average-depth setting works fine. A 24 ft round above ground pool filled to 4.3 ft holds about 14,650 gallons. A 15 x 30 ft oval above ground pool holds about 11,380 gallons at the same depth. The fill cost from a garden hose at $4 per 1,000 gallons is about $46-60.

Pool Water Calculator Chemicals

Once you know your pool water volume in gallons, chemical dosing is straightforward. A pool water calculator chemicals reference:

  - Liquid chlorine (10%): 10.5 oz per 10,000 gal raises free chlorine by 1 ppm

  - Granular cal-hypo (65%): 1.55 oz per 10,000 gal per 1 ppm

  - Muriatic acid (31.45%): 26 oz per 10,000 gal lowers pH by 0.2

  - Soda ash (pH up): 6 oz per 10,000 gal raises pH by 0.2

  - Baking soda (alkalinity up): 1.5 lb per 10,000 gal raises TA by 10 ppm

  - Cyanuric acid (stabilizer): 13 oz per 10,000 gal raises CYA by 10 ppm

  - Pool salt: 40 lb per 10,000 gal brings 0 ppm pool to ~3,200 ppm

Add chemicals in order: alkalinity first, pH second, cyanuric acid third, chlorine last. Wait at least 4 hours between doses.

Pool Water Calculator App vs Website

Looking for a pool water calculator app on your phone? Bookmark this page and pin it to your home screen; it works offline in any mobile browser. There is also a dedicated pool chemical calculator and a more detailed pool pump calculator for GPM and horsepower sizing. All three are free, no install required, and use the same formulas industry pool professionals use.

Swimming Pool Water Capacity Calculator Tips

A swimming pool water capacity calculator is only as accurate as your measurements. Two common mistakes:

  - Measuring outside instead of inside the pool. Always measure the actual water dimensions, waterline to waterline, not the outside of the coping or deck. That overstates volume by 10-20%.

  - Not averaging the depth properly. For pools with a shallow and deep end, average depth equals (shallow + deep) / 2, not the middle depth. A 3 ft shallow / 8 ft deep pool averages 5.5 ft, which matters because chemical doses scale linearly with volume.

## Frequently Asked Questions

**Q: How does a swimming pool water calculator work?**

A: A swimming pool water calculator multiplies surface area by average depth and by 7.48 (gallons per cubic foot). A 16 x 32 ft rectangle pool at 5 ft average depth is 16 x 32 x 5 x 7.48 = 19,150 gallons. For round, use pi x radius^2; for oval, use pi x (length/2) x (width/2); for kidney, use length x width x 0.85 x 7.0.

**Q: Is there an above ground pool water calculator option?**

A: Yes. An above ground pool water calculator uses the same shape formulas as in-ground. Most above ground pools are round or oval with a single flat depth, so choose Round or Oval and enter the single average depth. A 24 ft round at 52 in (4.33 ft) is pi x 12^2 x 4.33 x 7.48 = 14,650 gallons.

**Q: How do I use the pool water calculator oval setting?**

A: Select Oval, enter the longer dimension as Length and the shorter as Width, then enter average depth. The pool water calculator oval formula is pi x (Length/2) x (Width/2) x Depth x 7.48. A 12 x 24 ft oval at 4 ft deep is pi x 6 x 12 x 4 x 7.48 = about 6,770 gallons.

**Q: Is there a pool water calculator app I can install?**

A: You don't need a separate pool water calculator app. This page is a free web-based tool that works in any mobile browser. Save it to your phone's home screen for one-tap access. Many of the paid pool water calculator app listings use the exact same formulas you'll find here, just wrapped in a paid install.

**Q: How does this relate to pool water calculator chemicals dosing?**

A: A pool water calculator chemicals reference is built into the output: it shows how many ounces of 10% liquid chlorine raise free chlorine by 1 ppm at your pool's volume. For detailed dosing of pH up, pH down, alkalinity, cyanuric acid, and salt, use the dedicated Pool Chemical Calculator after you know the gallons from this page.

**Q: How much does a swimming pool water capacity calculator help with monthly cost?**

A: A swimming pool water capacity calculator tells you the top-up cost by multiplying the monthly evaporation (typically 2 inches per month in summer for uncovered pools) by your water rate. A 500 sq ft pool loses 500 x (2/12) x 7.48 = 624 gallons per month in summer, which is $2-3 at typical US water rates. A solar cover cuts that by about 50%.

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Source: https://vastcalc.com/calculators/everyday/pool-water
Category: Everyday Life
Last updated: 2026-04-08