Volume for a 15×30 Inground Pool
Free calculator with pre-filled dimensions • Updated March 2026
A 15×30 inground pool with 5.5 ft average depth holds approximately 18,514 gallons of water.
Open calculator with these dimensions →15×30 Inground Pool Volume Guide
A 15×30 foot rectangle is the most popular residential inground pool size in America. With a typical depth range of 3.5 to 8 feet (5.5 ft average), this pool holds approximately 18,514 gallons. Knowing your exact volume is essential for proper chemical dosing, heater sizing, and pump selection.
Volume by Average Depth
| Avg Depth | Gallons | Fill Time (garden hose) |
|---|---|---|
| 4 ft | 13,500 | 27–34 hours |
| 5 ft | 16,875 | 34–42 hours |
| 5.5 ft | 18,514 | 37–46 hours |
| 6 ft | 20,250 | 41–51 hours |
Chemical Dosing for 18,514 Gallons
| Chemical | Amount to Add | Purpose |
|---|---|---|
| Chlorine (liquid, 12.5%) | ~2.5 cups to raise 1 ppm | Sanitizer |
| pH increaser (soda ash) | ~5 oz to raise 0.1 | pH balance |
| Stabilizer (CYA) | ~2 lbs to raise 10 ppm | Chlorine protection |
| Salt (if saltwater) | ~560 lbs for 3,200 ppm | Chlorine generation |
Pro Tips
- Calculate average depth carefully. Average depth = (shallow end + deep end) ÷ 2 for a uniform slope. If the pool has a flat shallow section and a steep dive zone, calculate each section separately and add volumes.
- Heater sizing: For an 18,500-gallon pool, a 400,000 BTU gas heater raises temperature ~1°F per hour. A heat pump (140,000 BTU) takes about 3× longer but costs 70% less to operate.
- Pump turnover rate: Aim to circulate the full volume every 8 hours. 18,514 gallons ÷ 8 hours = 39 GPM minimum pump flow rate.
Frequently Asked Questions
How many gallons in a 15×30 pool?
With a 5.5-foot average depth, a 15×30 pool holds approximately 18,514 gallons. The formula is length × width × average depth × 7.48 (gallons per cubic foot).
How long to fill a 15×30 pool?
A standard garden hose delivers 400–500 gallons per hour. Filling 18,514 gallons takes 37–46 hours. Using a fire hydrant fill service ($200–$400) cuts this to 2–3 hours.