Pool Volume & Chemistry Calculator
Calculate your pool’s gallons, then balance your water chemistry
⭐ Bookmark this page — you’ll need it all season (ctrl D)
⚠️ Safety Rules — Read Before Adding Chemicals
- Rule #1: Always read product labels and follow instructions
- Rule #2: NEVER mix chemicals (including different types of chlorine)
- Rule #3: Never add water to chemical — always add chemical to water
Calculate Your Pool Volume
Note: These are estimates. Above-ground pools assume water level is ~4 inches below the wall top.
Balance Your Water Chemistry
Enter your test results. Adjust chemicals in order: Alkalinity → pH → Chlorine → Calcium → CYA
Recommendations
Ideal Chemical Ranges
| Chemical | Min | Ideal | Max |
|---|---|---|---|
| Free Chlorine | 1.0 | 1.0 – 4.0 | 5.0 |
| Combined Chlorine | 0 | 0 | 0.2 |
| Alkalinity | 80 | 80 – 120 | 120 |
| pH | 7.2 | 7.2 – 7.8 | 7.8 |
| Calcium Hardness | 150 | 150 – 250 | 400 |
| Cyanuric Acid | 30 | 30 – 60 | 100 |
| Salinity | 2,700 | 3,000 – 3,500 | 4,000 |
Quick Reference Charts
Above-Ground Round Pools
52″ Wall
| Size | Gallons |
|---|---|
| 12 ft | 3,398 |
| 15 ft | 5,310 |
| 18 ft | 7,646 |
| 21 ft | 10,408 |
| 24 ft | 13,594 |
| 27 ft | 17,205 |
| 30 ft | 21,240 |
| 33 ft | 25,700 |
48″ Wall
| Size | Gallons |
|---|---|
| 12 ft | 2,975 |
| 15 ft | 4,646 |
| 18 ft | 6,692 |
| 21 ft | 9,106 |
| 24 ft | 11,895 |
| 27 ft | 15,054 |
| 30 ft | 18,585 |
Above-Ground Oval Pools
52″ Wall
| Size | Gallons |
|---|---|
| 12′ × 24′ | 6,797 |
| 15′ × 30′ | 10,620 |
| 16′ × 32′ | 12,084 |
| 18′ × 33′ | 14,019 |
| 18′ × 40′ | 17,000 |
| 21′ × 43′ | 21,294 |
48″ Wall
| Size | Gallons |
|---|---|
| 12′ × 24′ | 5,948 |
| 15′ × 30′ | 9,293 |
| 16′ × 32′ | 10,574 |
| 18′ × 33′ | 12,267 |
In-Ground Pools (Rectangle/Roman)
Estimates based on 3.5′ shallow end
| Size | 4-6′ avg depth | 6-8′ avg depth |
|---|---|---|
| 12′ × 24′ | 9,000 | 11,000 |
| 14′ × 28′ | 12,300 | 15,000 |
| 15′ × 30′ | 14,100 | 17,200 |
| 16′ × 32′ | 16,000 | 19,500 |
| 18′ × 36′ | 20,300 | 24,700 |
| 20′ × 40′ | 25,000 | 30,500 |
| 22′ × 44′ | 30,300 | 36,900 |
| 25′ × 45′ | 35,200 | 42,900 |
| 25′ × 50′ | 39,000 | 47,600 |
Fiberglass Pools (Typical Ranges)
Volumes vary by manufacturer — check your shell specs for exact volume
| Size Category | Typical Gallons |
|---|---|
| Small (12×24) | 6,500–8,500 |
| Medium (14×30) | 10,000–13,000 |
| Large (16×36) | 14,000–18,000 |
| XL (16×40) | 16,000–21,000 |
| Sport (16×40 rectangle) | 18,000–22,000 |
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📝 Notes About These Ranges
Calcium Hardness by Pool Type: Plaster/concrete pools NEED calcium (200-400 ppm) — low calcium water will dissolve your pool surface. Vinyl and fiberglass pools can run lower because those surfaces don’t contain calcium, but the ranges shown protect your pump, filter, and other equipment.
Heaters Override Everything: If you have a gas or heat pump heater, maintain at least 200 ppm calcium regardless of pool type. Low calcium water corrodes heat exchangers — an expensive repair.
The CYA-Chlorine Relationship: Higher CYA means you need more chlorine to sanitize effectively. That’s why salt pools (60-80 ppm CYA) aren’t a problem — the salt cell constantly generates chlorine. But if you’re manually dosing chlorine, keep CYA closer to 30-50 ppm so your chlorine works harder.
Test Alkalinity First: Always adjust alkalinity before pH. Alkalinity acts as a buffer — if it’s off, your pH will bounce around no matter what you do.
Wait Before Retesting: After adding chemicals, run your pump for at least 8 hours before retesting. Chemistry takes time to stabilize.