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BuildMate
Outdoor

Pool Calculator USA 2026

Calculate pool volume in gallons and the chemicals needed to balance it — chlorine, muriatic acid and stabilizer.

Reviewed by BuildMate Editorial Team Construction Researchers Updated March 2026 2 min read Fact-checked

Used by

250,000+ homeowners

Avg. time

~15 seconds

Updated

2026

Accuracy

Pro estimation

Works on: Desktop Tablet Mobile No registration required
Unit system

Enter your measurements

Results

Pool volume

29,920 gallons

Shock chlorine (cal-hypo)

3.0 lb

Cyanuric acid (stabilizer 30 ppm)

7.5 lb

Calculation steps
  1. 1.Volume = 40 × 20 × 5 = 4000 ft³
  2. 2.Gallons = 4000 × 7.48 = 29,920

Includes a standard waste allowance. Verify with your supplier before ordering.

Stored on this device — no account needed.

What this calculator does

Sizes the materials for outdoor structures — deck boards, joists, posts or fence panels — with proper spans and waste built in.

When to use it

  • Building a deck, fence, pergola or gazebo.
  • Replacing rotted deck boards or fence pickets.
  • Planning a backyard remodel.

Common mistakes

  • Undersizing joists for the deck span.
  • Skipping post footings below the frost line.
  • Buying pressure-treated lumber wet and installing immediately.

Pro tips

  • Let PT lumber dry 2–4 weeks before staining.
  • Use hot-dipped galvanized or stainless fasteners.
  • Pull a permit for anything above 30" off grade.
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Disclaimer: Estimates based on 2026 RSMeans USA data. Actual quantities vary by site conditions, waste and installer practices. Verify with your supplier or contractor before ordering.

How it works

  1. 1Enter length, width and average depth in feet.
  2. 2We convert to gallons (1 ft³ = 7.48 gal).
  3. 3Chemical doses assume a standard 3 ppm chlorine shock.

Formula

Rectangular Gallons = L × W × Avg Depth × 7.48

Worked example

20 × 40 × 5 ft = 4,000 ft³ × 7.48 = 29,920 gallons.

Frequently asked questions

What's the ideal free chlorine?

1–3 ppm for a residential pool.

How often to shock?

Weekly, or after heavy use / a rainstorm.

Is the Pool Calculator free to use?

Yes — every BuildMate calculator is 100% free, requires no signup and works offline once the page has loaded.

How accurate are these estimates?

Formulas follow 2026 industry standards (RSMeans, ICC and manufacturer specs). Real-world results vary by site conditions, waste and installer practices — always get 2–3 written quotes from licensed pros before committing.

Can I save my calculation?

Yes. Hit the Save button after you run an estimate — it's stored on this device (no account needed) and you can access it anytime from the Saved drawer.

Can I compare two projects side-by-side?

Yes. Add estimates to Compare and open the Compare drawer to see them side-by-side, then use Download PDF or Email to share the comparison.

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