Above-Ground Pool Volume Calculator
Calculate the water volume of any round or oval above-ground pool in gallons and litres. Enter inner wall-to-wall measurements and uniform depth ? results display instantly.
Above-Ground Pool
How to Use This Above-Ground Pool Volume Calculator
Select Imperial for measurements in feet and results in US gallons (gal), or Metric for metres and litres (L). US and Canadian pool owners should use Imperial. Australian, UK, and European owners should select Metric.
- Shape (Round / Oval) ? choose the shape that matches your pool. Round is the default; switch to Oval for elongated above-ground pools.
- DIAMETER (D) ? for round pools, enter the inner wall-to-wall measurement in feet or metres. Measure straight across the pool through the centre. Do not use the size printed on the box; it describes the outer frame and will overestimate volume by 8?12%.
- LENGTH (L) and WIDTH (W) ? for oval pools, enter the longest and shortest inner wall-to-wall distances.
- WATER DEPTH ? measure from the waterline down to the pool floor. Above-ground pools have a flat bottom, so one depth measurement is all you need.
Results display in gallons, litres, and cubic feet (or cubic metres in Metric mode) simultaneously. Use the calculated volume for chemical dosing, pump flow-rate sizing, heater BTU estimates, and salt-cell calibration.
Manufacturer box dimensions describe the outer frame ? the inner water area is 6?8 inches smaller per side, reducing the actual volume by 8?12% compared to the advertised pool size.
What Makes Above-Ground Pool Volume Calculation Different
Above-ground pools differ from inground pools in 3 ways that affect volume calculation. First, the shape is almost always round or oval ? the formula uses the ?/4 factor (0.7854) for both. Second, the bottom is flat, so the pool has one uniform depth. No average-depth estimation is needed.
Third, manufacturer dimensions describe the outer shell, not the inner water area. A pool sold as ?18 ft? typically measures 17 ft 4 in to 17 ft 6 in wall to wall inside the frame. Always measure inner wall to inner wall for accurate volume. Ignoring this difference on an 18 ft round pool overstates volume by roughly 600?900 gallons (2,270?3,400 L), enough to throw off chlorine dosing by a full dose unit.
Above-Ground Pool Volume ? Common Sizes Reference
The table below lists water volume for the most common above-ground pool sizes at standard wall depths of 48 inches (4 ft) and 52 inches (4.33 ft).
| Pool Size | Shape | Wall Depth | US Gallons | Litres |
|---|---|---|---|---|
| 12 ft | Round | 48 in (4 ft) | 3,384 | 12,810 |
| 12 ft | Round | 52 in (4.33 ft) | 3,666 | 13,878 |
| 15 ft | Round | 48 in (4 ft) | 5,288 | 20,016 |
| 15 ft | Round | 52 in (4.33 ft) | 5,728 | 21,684 |
| 18 ft | Round | 48 in (4 ft) | 7,614 | 28,823 |
| 18 ft | Round | 52 in (4.33 ft) | 8,249 | 31,225 |
| 24 ft | Round | 48 in (4 ft) | 13,536 | 51,241 |
| 24 ft | Round | 52 in (4.33 ft) | 14,664 | 55,511 |
| 12 ? 20 ft | Oval | 48 in (4 ft) | 5,640 | 21,350 |
| 15 ? 30 ft | Oval | 48 in (4 ft) | 10,575 | 40,032 |
| 18 ? 33 ft | Oval | 52 in (4.33 ft) | 15,123 | 57,246 |
Calculated using D? ? Depth ? ?/4 (round) or L ? W ? Depth ? ?/4 (oval). Gallons = cubic feet ? 7.48052. Litres = cubic feet ? 28.3168.
Above-ground pool volumes in this table range from <strong>3,384 gallons (12,810 L)</strong> for a 12 ft round to <strong>15,123 gallons (57,246 L)</strong> for an 18 ? 33 ft oval. Wall depth adds 8?9% more volume per additional 4 inches. Enter your exact inner diameter and water depth in the calculator above for pools not listed here.
How to Calculate Above-Ground Pool Volume by Shape
Pool shape determines which formula applies. Round above-ground pools use D? ? Depth ? ?/4, which accounts for the circular area inside a square bounding box. Oval above-ground pools use L ? W ? Depth ? ?/4, applying the same ellipse factor. This calculator handles both shapes automatically based on your inputs.
Worked example ? 18 ft round pool, 48-inch (4 ft) wall depth: 18? = 324. Multiply 324 ? 4 = 1,296. Multiply 1,296 ? 0.7854 (?/4) = 1,017.88 cubic feet. Multiply 1,017.88 ? 7.48052 = 7,614 gallons (28,823 litres).
For oval above-ground pools, use Length ? Width instead of Diameter?. A 15 ? 30 ft oval at 48 inches depth holds 10,575 gallons (40,032 L). Find the right calculator for your pool shape at pool volume calculator by shape, or see all pool volume formulas with step-by-step explanations at pool volume formulas.
Frequently Asked Questions
What is the most accurate way to calculate above-ground pool volume?
Measure the inner diameter wall to wall, then apply D? ? Depth ? ?/4 ? 7.48052 for gallons. A 15 ft inner-diameter pool at 48 inches (4 ft) of water depth holds 5,288 gallons (20,016 L). Use a tape measure across the centre of the pool at the waterline ? not the outer frame or top rail. Round the measurement to the nearest inch for best accuracy.
Why does the calculated volume differ from the size printed on my pool box?
The number on the box describes the outer frame dimension, not the inner water area. A pool sold as 18 ft measures roughly 17 ft 4 in to 17 ft 6 in inside the frame rails. That 6?8 inch difference per side reduces actual water volume by 8?12% compared to the advertised size. On an 18 ft round pool at 4 ft depth, the box-based calculation overstates volume by approximately 600?900 gallons (2,270?3,400 L).
How many gallons does an 18 ft round above-ground pool hold?
7,614 gallons (28,823 L) at 48 inches (4 ft) wall depth, or 8,249 gallons (31,225 L) at 52 inches (4.33 ft) wall depth. These figures use the inner diameter of 18 ft. Actual water depth is typically 2?4 inches less than the wall height because the waterline sits below the top rail ? an 18 ft pool filled to a 44-inch waterline holds closer to 7,000 gallons (26,498 L).
Do above-ground pools need average depth calculation?
No. Above-ground pools have a flat bottom, so there is no slope from shallow end to deep end. Enter the single water depth in the Water Depth field; the calculator uses that value directly. The one exception: a pool sitting on uneven ground may have 1?3 inches of depth variation from one side to the other. Measure both sides and use the average for a corrected result.
Can I use this calculator for an Intex or Bestway pool?
Yes. Intex, Bestway, and Coleman above-ground pools are standard round or oval shapes. The same D? ? Depth ? ?/4 formula applies. Note that Intex and Bestway dimensions on the packaging describe the outer frame. Subtract approximately 4?6 inches from each side to estimate the inner water diameter, or measure from inner wall to inner wall directly. An Intex 15 ft pool typically measures about 14 ft 4 in inside, reducing calculated volume by roughly 9%.
How often should I recalculate my above-ground pool volume?
Recalculate when 3 conditions occur: the water level drops or rises by 2 or more inches from the original waterline, the pool has been drained and refilled (water depth may differ from the first fill), or chemical dosing errors keep happening despite following label directions. A 2-inch water level change in an 18 ft round pool shifts the volume by approximately 350 gallons (1,325 L) ? enough to affect chlorine concentration by 0.3?0.5 parts per million (ppm).