Pool Volume Calculator
Estimate the water volume of your swimming pool in gallons. Supports rectangular and round pools with varying depths. Useful for chemical dosing, filling time estimates, and water cost.
Knowing your pool's volume is essential for chemical dosing (chlorine, pH balancers, algaecide), filling estimates (time and cost), and basic pool maintenance. A standard 30 × 15 ft inground pool with average depth of 5.5 ft holds about 18,500 gallons; an above-ground pool might hold 5,000-15,000 gallons depending on size. Chemical doses are typically calculated per 10,000 gallons, so accurate volume matters.
This calculator returns water volume in gallons for rectangular and round pools, accounting for sloped bottoms (shallow + deep end averaging). The standard formula multiplies dimensions: length × width × average depth × 7.48 gallons/cu ft. For rectangular pool with sloped bottom, use the average of shallow and deep end depths. For round pools, area is π × (diameter/2)².
Beyond volume, the calculator also estimates filling cost. Water utilities charge $3-12 per 1000 gallons. A 20,000-gallon pool fill costs $60-240 (more during drought or summer in some areas). Garden hose flow rates average 9-12 gallons per minute, so filling 20,000 gallons takes 25-40 hours. Truck delivery is faster but costs $200-600 for a typical pool.
Inputs
Results
Pool Volume
18,514 gal
Average Depth
5.5 ft
Fill Cost
$92.57
Pool Details
| Measurement | Value |
|---|---|
| Pool Dimensions | 30 x 15 ft |
| Average Depth | 5.5 ft (3' - 8') |
| Volume (cubic feet) | 2,475 |
| Volume (gallons) | 18,514 |
| Volume (liters) | 70,084 |
| Fill Time (garden hose) | ~34.3 hours (1.4 days) |
| Water Cost to Fill | $92.57 |
| Chlorine (initial dose) | ~11 oz of liquid chlorine |
Formula
How to use this calculator
- Enter pool length and width in feet.
- For sloped bottoms, enter both shallow and deep end depths.
- Toggle "Round Pool" for circular pools.
- Enter water cost per 1000 gallons.
- Calculator returns gallons and filling cost estimate.
- Use the gallon count for chemical dosing calculations.
Worked examples
Standard backyard pool
**Scenario:** 30 × 15 ft rectangular pool with 3 ft shallow end and 8 ft deep end. Need to fill for the season. **Calculation:** Average depth: (3+8)/2 = 5.5 ft. Volume: 30 × 15 × 5.5 = 2475 cu ft = 18,513 gallons. At $5/1000: $93 to fill. Time at 10 GPM garden hose: 30.9 hours = ~1.3 days. **Result:** 18,500 gallons in a typical backyard pool. Fill cost: $93. Filling time: 1.3 days with garden hose, < 2 hours with truck delivery ($200-400 cost). Garden hose strategy: leave running overnight, check periodically for leaks.
Above-ground round pool
**Scenario:** 24 ft round above-ground pool with 4 ft constant depth. **Calculation:** Area: π × 12² = 452 sq ft. Volume: 452 × 4 = 1810 cu ft = 13,533 gallons. At $5/1000: $68 to fill. Filling time at 10 GPM: 22.5 hours. **Result:** 13,500 gallons in 24-ft round above-ground pool. Smaller than inground but easier to install/remove. Chemical dosing for 13,500 gal pool: 1.35 lbs chlorine shock per dose (15 ppm), 0.7 oz algaecide weekly.
Large family pool
**Scenario:** 20 × 40 ft rectangular pool with diving area: 3 ft shallow, 10 ft deep. **Calculation:** Average depth: (3+10)/2 = 6.5 ft. Volume: 20 × 40 × 6.5 = 5200 cu ft = 38,896 gallons. At $5/1000: $194 to fill. Time at 10 GPM: 65 hours = 2.7 days. **Result:** ~39,000 gallons in large family pool. Filling time substantial — truck delivery makes sense ($300-500). Chemical dosing scales: 3.9 lbs chlorine shock per dose, larger filter required (40+ GPM minimum). Monthly chemical cost: $80-150 for proper maintenance.
When to use this calculator
**Calculate pool volume for:**
- **Initial filling**: estimating water bill and filling time. - **Refilling after partial drain**: chemistry rebalance. - **Chemical dosing**: always per 10,000 gallon basis. - **Filter sizing**: GPM needed for proper turnover. - **Pump sizing**: GPM and pressure requirements. - **Heater sizing**: heating capacity needed. - **Insurance assessments**: pools require liability coverage.
**Pool design considerations:**
- **Depth**: shallow end 3 ft minimum; deep end 5-8 ft for diving. - **Slope**: gradual transition from shallow to deep is most popular. - **Steps and ramps**: easy entry for older users and children. - **Tanning ledge**: shallow ledge for chairs and sun. - **Spa connection**: shared filtration and heating.
**Pool types and lifespans:**
| Type | Lifespan | Install cost | |---|---|---| | Above-ground | 7-15 years | $1,500-5,000 | | Inground concrete | 30+ years | $30,000-80,000 | | Inground fiberglass | 20-30 years | $20,000-50,000 | | Inground vinyl liner | 20+ years (liner: 7-15) | $20,000-40,000 | | Saltwater conversion | Same as base + 20 years | +$3000-5000 |
**Cost of pool ownership (annual):**
- **Electricity (pump, heater)**: $1500-3000. - **Water (refilling, evaporation)**: $300-800. - **Chemicals**: $400-800. - **Maintenance**: $300-1500. - **Insurance**: $400-1000. - **Total annual**: $3000-7000.
**Maintenance frequency by pool size:**
- **Small (< 10,000 gal)**: 30 min/week for routine maintenance. - **Medium (10-20,000 gal)**: 1-2 hours/week. - **Large (20-30,000 gal)**: 2-3 hours/week. - **Very large (30+)**: 3-5 hours/week, often professional service.
**Common pool problems:**
- **Algae**: green water, slimy walls. Treat with shock chlorine. - **Cloudy water**: imbalanced chemistry or fine particles. Adjust pH/alkalinity, clean filter. - **Stains**: copper (turquoise), iron (brown), organic (green). Specific treatments per stain type. - **Equipment failure**: pump, filter, heater all have wear lives. - **Cracks**: concrete shells crack from settling or freeze-thaw.
**Seasonal considerations:**
- **Opening (spring)**: remove cover, balance chemistry, clean. - **Mid-season**: routine maintenance, periodic deep cleaning. - **Closing (fall)**: drain to below skimmer, winterize equipment, cover. - **Winter (closed)**: minimize freeze damage, periodic checks.
**Chemistry basics:**
- **Test water 2-3× per week**: pH and chlorine minimum. - **Shock weekly**: high-dose chlorine to break down chloramines. - **Balance alkalinity first**: stabilizes pH. - **Add stabilizer (CYA)**: protects chlorine from UV breakdown. - **Adjust calcium hardness**: prevents corrosion and scaling.
**Safety considerations:**
- **Fencing**: required by code in most jurisdictions. - **Self-closing/latching gates**. - **Alarms**: pool alarms required in many jurisdictions. - **Lighting**: for after-dark use. - **Lifeguard for parties**: especially with non-swimmers. - **GFCI protection**: required for pool electrical.
**Energy efficiency:**
- **Variable speed pumps**: 70-80% energy savings vs single-speed. - **Solar covers**: reduce evaporation 90% + heat gain. - **LED lighting**: replaces incandescent. - **Heat pumps**: more efficient than gas heating. - **Solar pool heaters**: free heating from sun.
**Tax and insurance implications:**
- Pools typically don't qualify for property tax deductions. - Homeowner insurance may exclude or limit pool liability. - Umbrella insurance often recommended. - Some jurisdictions tax pool value as property addition.
Common mistakes to avoid
- Confusing pool volume with surface area. Volume is 3D; surface is 2D.
- Using only shallow or only deep depth. Use average for sloped bottoms.
- Forgetting cubic foot to gallon conversion. 1 cu ft = 7.48 gallons.
- Overdosing chemicals for incorrect volume. Always recalculate after pool changes.
- Trying to fill with single garden hose for large pool. Use multiple hoses or truck for large pools.
- Underestimating filling cost. $0.50-1+ per 100 gallons typical; 20K gallons = $100-200.
- Forgetting evaporation. Pools lose 1/4" per day to evaporation; 1/2" in hot/windy conditions.