How many gallons in a 15x30 pool?

About 12,700 gallons with a 4 to 6 ft depth (5 ft average). Add 10% for uneven bottoms or irregular shapes.

How long does it take to fill a pool?

A garden hose delivers about 500 gallons per hour. A 15,000-gallon pool takes roughly 30 hours. Fire department tankers can do it in 2 to 3 hours but cost $200 to $500.

How much does it cost to fill a pool with water?

$50 to $150 for a 15,000-gallon pool using municipal water at $0.005 to $0.01 per gallon. Rates vary by city and region.

How much chlorine do I need for my pool?

2 ounces of liquid chlorine per 10,000 gallons for shock treatment. Maintain 1 to 3 ppm free chlorine for daily swimming.

How much salt for a saltwater pool?

About 50 pounds of pool salt per 2,000 gallons to reach 3,200 ppm. A 15,000-gallon pool needs roughly 375 lbs of salt.

What shape pool holds the most water?

Rectangular pools hold the most water for a given footprint. Kidney and freeform shapes hold about 75% as much as an equivalent rectangle.

How do I measure pool depth?

Use a weighted line or pool pole at the shallow end, middle, and deep end. Average the readings. For sloped bottoms, use the shallow and deep end average.

How do I calculate an irregular shaped pool?

Divide the pool into simpler shapes like rectangles and circles. Calculate each section separately and add the volumes together.

UtilityPool Volume Calculator

Pool Volume Calculator

Calculate pool gallons, liters, fill time, pump flow, water weight, and startup estimates.

Pool Details

Pool shape

Most lap and backyard pools.

Length (ft)

Width (ft)

Shallow depth (ft)

Deep depth (ft)

Ready to calculate

Enter pool dimensions for volume estimates.

Last updated June 5, 2026 by our expert review team

Pool Volume by Size

Plunge (8 x 12 ft)2,700 gal

Small (12 x 24 ft)6,500 gal

Medium (16 x 32 ft)15,400 gal

Standard (20 x 40 ft)24,000 gal

Large (20 x 44 ft)26,400 gal

Use this as a scale check before fill, pump, or chemical planning. Actual water volume changes with depth, shape, benches, steps, and ledges.

Expert Contributors

Creator

Cherry Jane Limbago

Licensed Civil Engineer & Master Plumber

Cherry Jane Limbago

Licensed Civil Engineer & Master Plumber

Licensed civil engineer and master plumber with 10+ years in structural design, estimation, and project management. Currently Project Engineer at Universal Robina Corporation.

See full profile

Expert Review

Hawkin

Certified Cost & Estimating Professional

Hawkin

Certified Cost & Estimating Professional

AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.

See full profile

Updated June 2026

How we verify our calculators

Pool Shape and Depth Guide

Pool volume depends on the top-view shape and the average water depth. Steps, benches, and ledges reduce the actual water volume.

Pool volume guide showing pool shape choice, average depth, gallons, fill time, circulation sizing, and dosing after testing.

Use the visual as a planning path. Always test water and follow the pool chemical label before dosing.

Pro Tips

Use average depth for sloped pools. Add shallow depth and deep depth, then divide by 2.

Freeform pools are estimates. Benches, steps, tanning ledges, and irregular curves can change actual water volume.

Dose chemicals after testing the water. Volume gives the starting point, but test results decide the actual adjustment.

A garden hose often fills around 500 gallons per hour. Large pools can take more than two days from empty.

Planning a deck around the pool? Use the concrete slab calculator for the surrounding pad or patio.

How the Calculator Works

The calculator converts the selected shape into cubic feet, then multiplies by 7.48052 gallons per cubic foot. Metric inputs are converted internally before the gallon and liter outputs are calculated.

Average depth

(shallow + deep) / 2

Rectangle gallons

L x W x avg depth x 7.48052

Round gallons

pi x radius^2 x avg depth x 7.48052

Quick Reference

1 cu ft: 7.48052 gal
1 gallon: 3.78541 L
Water weight: 8.34 lb/gal
Garden hose: about 500 gal/hr
Turnover check: 8 hours
Salt target: about 3,200 ppm

Real-World Pool Examples

Above-ground round

15 ft diameter, 4 ft depth

5,288 gal

Popular above-ground size. Fill time is about 10.6 hours at 500 gal/hr.

Default rectangle

30 x 15 ft, 3 to 8 ft depth

18,515 gal

A common in-ground pool with sloped depth.

Large rectangle

40 x 20 ft, 4 to 8 ft depth

35,906 gal

Large pools can take about 72 hours from a garden hose.

Kidney/freeform

40 x 20 ft, 4 to 8 ft depth, 0.75 factor

26,930 gal

Freeform factor prevents overestimating chemical needs.

Pool Volume Calculator FAQ

How do I calculate pool gallons?

Find cubic feet from the pool shape, then multiply by 7.48052 gallons per cubic foot.

How do I measure average pool depth?

Add shallow depth and deep depth, then divide by 2. Flat-bottom pools use the same value for both fields.

How many gallons are in a 15 ft round pool?

At 4 ft deep, a 15 ft round pool holds about 5,288 gallons.

Why is kidney pool volume lower?

Curved freeform pools hold less water than the full rectangle around them. This calculator uses a 0.75 planning factor.

Can I dose chemicals from this number?

Use the volume as a starting point, then test water and follow the product label. Do not dose from volume alone.

How long does a pool take to fill?

Divide gallons by fill rate. At 500 gal/hr, an 18,500 gallon pool takes about 37 hours.

Pool Volume Mistakes

Using only the deep end

This overestimates water volume. Average shallow and deep depths for a sloped pool.

Ignoring steps and benches

Built-in features displace water and reduce actual volume.

Treating freeform as a rectangle

Use a shape factor or split the pool into smaller shapes.

Dosing before testing

Volume helps with the starting estimate. Test results and product labels decide the final dose.

Important Disclaimer

These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.