Why do I need to know pool volume?

Chemical dosing (chlorine, pH adjusters, algaecides) is calculated per gallon of water — using the correct volume is essential for safe, effective, and cost-efficient pool chemistry, since under- or over-dosing both cause problems.

Which formula does each shape use?

Each one finds the water surface seen from above and multiplies it by the depth. A rectangle is length times width. A round pool is π times the diameter squared, divided by four. A true ellipse is π times half the length times half the width. An oval with straight sides is two half-circles the pool's width across, joined by a rectangle as long as the straight run. A kidney is 0.45 times the two lobe widths added together, times the length. The circle, the ellipse and the kidney are the forms in the Pool & Hot Tub Alliance's operator handbook; the straight-sided oval is plain geometry.

Why do pool charts give different factors for an oval pool?

Because the trade uses the word for two shapes. The Pool & Hot Tub Alliance's handbook works an oval as a true ellipse, which covers π/4, about 0.785, of the rectangle it fits in. Hayward's quick start guide multiplies length × width × depth by 6.7 for an oval where it uses 7.5 for a rectangle, which is 0.893 of the rectangle: to the three figures Hayward prints, what an oval with straight sides and half-circle ends covers when it is twice as long as it is wide, the common above-ground pool. Hayward does not say which oval it means. Choose the shape that matches the pool rather than the factor; a straight-sided oval worked as an ellipse comes out about an eighth short at that proportion.

How do I measure a kidney-shaped pool?

Three measurements: the overall length from the end of one lobe to the end of the other, and the width straight across each lobe at its widest, square to that length. The handbook's formula takes the water surface as 0.45 times Width A plus Width B, times the Length, and refers to a figure for where they are measured that is not reproduced here; the page uses their usual reading, the widths across the two lobes. A lobe wider than the length is flagged, since the length is the longest dimension. That factor is a rule of thumb for the usual kidney outline rather than a property of every kidney, so a pool with a deep waist or unusually full lobes can be noticeably different; where the dose has to be right, a meter on the fill tells you the real figure.

How do I handle a pool with a sloped bottom?

Choose the sloping floor and enter the water depth at the shallow end wall and at the deep end wall; the page works the volume at their average, the way the operator handbook does, and gives that answer at medium confidence. That is exact when the floor falls evenly from one end wall to the other. On the usual pool, a long flat shallow area and a short deep hopper, the plain average overstates the water: split the pool into a shallow section and a deep section, work each at its own depth, and add them.

How many US gallons are in a cubic foot?

Exactly 1,728 ÷ 231 = 7.4805, because a cubic foot is 1,728 cubic inches and a US gallon is defined as 231, and that is the figure this page multiplies by. The handbook and many quick charts round it to 7.5, which reads about a quarter of a per cent high. Until version 1.1.0 this page used 7.48, which read 0.007% low and printed a 10 by 5 m (32.8 by 16.4 ft) pool 1.5 m (4.9 ft) deep, 75 cubic metres, as 74,990 litres (19,811 US gallons); it now reads 75,000 litres (19,813 US gallons).

Pools & Water Features

Pool Volume Calculator (Rectangular, Round, Oval or Kidney)

The water a rectangular, round, oval or kidney-shaped pool holds over a flat or sloping floor, in litres or US gallons, for dosing and filling it.

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Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

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Imperial · sales tax

Pool Shape

The outline of the water surface seen from above.

Pick the outline that matches the water from above. An oval comes two ways: a true ellipse curves all the way round, while most above-ground ovals and plenty of in-ground ones have two straight sides with a half-circle at each end, and that one holds more water for the same length and width. A shape not listed, such as an L or a freeform, can be split into pieces this page does take, worked one at a time and added together.

Pool Length

The length of the pool.

Measure the water surface length, inside the walls rather than over the coping.

Pool Width

The width of the pool.

Measure perpendicular to the length.

Floor

Work the volume at one depth, or at the average of a shallow end and a deep end.

Most above-ground pools and many plunge and lap pools are one depth throughout. A pool that runs down from a shallow end to a deep end is worked the way the Pool & Hot Tub Alliance's operator handbook works it: at the average of the two end depths.

Average Depth

The water depth, or the average depth if you already know it.

Measure from the water line, which usually sits a little below the coping or the top of the wall, down to the floor. For a pool with a consistent depth (like most above-ground pools), use that single depth; for one with a shallow end and a deep end, choose the sloping floor instead and enter both.

Estimated pool volume

20,370 gallons

High confidence

A rectangle's water surface is its length times its width. The depth entered is applied across the whole of that area. The volume is that area times the depth.

Volume in cubic feet: 2,722.5 ft³
Water surface area: 544.5 sq ft
Depth the volume is worked at: 5 ft

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

Pool volume (gallons) = length x width x average depth (all in ft) x 7.4805 US gallons per cubic ft, the exact 1,728 ÷ 231 (a US gallon is 231 cubic inches)
Pool & Hot Tub Alliance (PHTA), Pool & Spa Operator Handbook (© 2021), Appendix B-4, Conversion & Calculation Guide: Average Depth = (Shallow Depth + Deep Depth) ÷ 2; Volume Circle (gallons) = 3.14 × radius × radius × Avg. Depth × 7.5; Volume Oval (gallons) = Short Radius × Long Radius × 3.14 × Avg. Depth × 7.5; Volume Kidney (gallons) = (Width A + Width B) × Length × 0.45 × Avg. Depth × 7.5, dimensions in feet, with a reference to the handbook's Figure 3-3 for the kidney (not reproduced here). This page uses π for 3.14 and the exact 7.4805 US gallons per cubic foot for 7.5
Hayward, Chemistry Quick Start Guide (092510 Rev A), Step 1, Calculate Pool Volume: rectangular L × W × average depth × 7.5 (gallons, feet) or × 1000 (litres, metres); round D × D × average depth × 5.9 or × 785; oval L × W × average depth × 6.7 or × 893
Plane geometry of an oval with straight sides: two half-circles of diameter W joined by a W × (L − W) rectangle cover W(L − W) + πW²/4, which at L = 2W is (1 + π/4)/2 = 0.893 of L × W; 0.893 × 7.5 = 6.70, which matches, to the figures printed, the 6.7 Hayward's guide gives an oval (Hayward does not say which oval it means)

Inputs used

Pool Shape: Rectangle
Pool Length: 33 ft
Pool Width: 16.5 ft
Pool Diameter: 18 ft
Oval Length, End to End: 30 ft
Oval Width, Side to Side: 15 ft
Overall Length, Including Both Rounded Ends: 30 ft
Width Between the Straight Sides: 15 ft
Kidney Length, End to End: 30 ft
Width Across the Larger Lobe (A): 15 ft
Width Across the Smaller Lobe (B): 11.5 ft
Floor: One depth: a flat floor, or an average depth you already know
Average Depth: 5 ft
Shallow-End Water Depth: 3.5 ft
Deep-End Water Depth: 6.5 ft

Intermediate steps

Volume in cubic feet: 2,722.5 ft³
Water surface area: 544.5 sq ft
Depth the volume is worked at: 5 ft

Final result20,365.71 gallons

Confidence note: A rectangle's water surface is its length times its width. The depth entered is applied across the whole of that area. The volume is that area times the depth.

What this calculation does not cover

One depth is applied across the whole plan, whether it is typed in or worked from the two ends. Averaging the shallow-end and deep-end figures is exact only where the floor falls at one steady rate from end wall to end wall, or where the shallow and deep sections cover equal plan area. On the usual arrangement - a large flat shallow section, a slope, then a smaller deep end - the plain average overstates the volume, and everything built on that figure inherits the overstatement in the same direction.
Nothing inside the outline is deducted. Steps, benches, tanning ledges, swim-outs, beach entries and coved or radiused corners all occupy space this calculation fills with water. A plan that is none of the five shapes here - an L, a lazy L, a Roman or Grecian end, a true freeform - is outside the model; split it into pieces the page does take, work each at its own depth and add them.
Only the water standing in the pool basin is counted. Pipework, skimmers, the filter, the heater and any attached spa, balance tank or vanishing-edge catch basin hold further water that circulates through the system and has to be dosed with it, and none of that appears in this figure.
This is a capacity estimate, not a dosing instruction. How much of any product to add depends on its active strength, your current test readings and your target concentration, and an overstated volume overdoses every time it is used. Dose once, circulate a full turnover, then test before dosing again - never dose twice off the same volume figure.
The fill itself is not covered: no source flow rate, no fill time, no metered water cost, and no account of the hardness, alkalinity or metal content of the incoming water, which is what sets the pool's starting chemistry and how much correction it needs on day one.

Estimated cost — your price

Price per gallon ($)

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Part of a bigger job

This trade is one line of a job takeoff. Run the whole job and every other trade comes back with it, off the same measurements.

Pool surround Check a quote
also measuresPool Cover & Liner Area Paver Paver Edging

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-10-05 · v1.1.0

Regulatory standards & verification citations4

Pool volume (gallons) = length x width x average depth (all in ft) x 7.4805 US gallons per cubic ft, the exact 1,728 ÷ 231 (a US gallon is 231 cubic inches)
Pool & Hot Tub Alliance (PHTA), Pool & Spa Operator Handbook (© 2021), Appendix B-4, Conversion & Calculation Guide: Average Depth = (Shallow Depth + Deep Depth) ÷ 2; Volume Circle (gallons) = 3.14 × radius × radius × Avg. Depth × 7.5; Volume Oval (gallons) = Short Radius × Long Radius × 3.14 × Avg. Depth × 7.5; Volume Kidney (gallons) = (Width A + Width B) × Length × 0.45 × Avg. Depth × 7.5, dimensions in feet, with a reference to the handbook's Figure 3-3 for the kidney (not reproduced here). This page uses π for 3.14 and the exact 7.4805 US gallons per cubic foot for 7.5
Hayward, Chemistry Quick Start Guide (092510 Rev A), Step 1, Calculate Pool Volume: rectangular L × W × average depth × 7.5 (gallons, feet) or × 1000 (litres, metres); round D × D × average depth × 5.9 or × 785; oval L × W × average depth × 6.7 or × 893
Plane geometry of an oval with straight sides: two half-circles of diameter W joined by a W × (L − W) rectangle cover W(L − W) + πW²/4, which at L = 2W is (1 + π/4)/2 = 0.893 of L × W; 0.893 × 7.5 = 6.70, which matches, to the figures printed, the 6.7 Hayward's guide gives an oval (Hayward does not say which oval it means)

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Pool Circulation and Water Balanceuses this calculator
Turnover time sets pump duty, filter area, pipe size, chemical demand and running cost — size it once, honestly, and the rest of the plantroom follows.
Hot Tub Volume, and Why Every Dose Depends On It
Sizing a Water Feature's Pump

Already have some? What size pool holds my gallons or litres?

How to calculate pool volume (rectangular, round, oval or kidney) in 16 steps

Pool ShapeThe outline of the water surface seen from above.
Pool LengthThe length of the pool.
Pool WidthThe width of the pool.
Pool DiameterStraight across the water surface, through the centre.
Oval Length, End to EndThe longest distance across the water, from the inside of one end to the inside of the other.
Oval Width, Side to SideThe widest distance across the water, at right angles to the length, through the middle.
Overall Length, Including Both Rounded EndsFrom the inside of one rounded end to the inside of the other.
Width Between the Straight SidesAcross the pool between its two straight sides, which is also the diameter of each rounded end.
Kidney Length, End to EndThe longest distance across the water, from the end of one lobe to the end of the other.
Width Across the Larger Lobe (A)The widest distance across the bigger rounded end, at right angles to the length.
Width Across the Smaller Lobe (B)The widest distance across the smaller rounded end, at right angles to the length.
FloorWork the volume at one depth, or at the average of a shallow end and a deep end.
Average DepthThe water depth, or the average depth if you already know it.
Shallow-End Water DepthWater depth at the shallow end wall, from the water line to the floor.
Deep-End Water DepthWater depth at the deep end wall.
Estimated pool volumeThe tool computes the estimated pool volume from those figures and shows the formula, its sources, and a confidence rating alongside it.

Estimated pool volume by pool length

Page defaults, not your figures above.

Pool Length	Estimated pool volume (gallons)
20 ft	12,078
30 ft	18,117
40 ft	24,156
50 ft	30,195
60 ft	36,234

Frequently asked questions

Why do I need to know pool volume?: Chemical dosing (chlorine, pH adjusters, algaecides) is calculated per gallon of water — using the correct volume is essential for safe, effective, and cost-efficient pool chemistry, since under- or over-dosing both cause problems.
Which formula does each shape use?: Each one finds the water surface seen from above and multiplies it by the depth. A rectangle is length times width. A round pool is π times the diameter squared, divided by four. A true ellipse is π times half the length times half the width. An oval with straight sides is two half-circles the pool's width across, joined by a rectangle as long as the straight run. A kidney is 0.45 times the two lobe widths added together, times the length. The circle, the ellipse and the kidney are the forms in the Pool & Hot Tub Alliance's operator handbook; the straight-sided oval is plain geometry.
Why do pool charts give different factors for an oval pool?: Because the trade uses the word for two shapes. The Pool & Hot Tub Alliance's handbook works an oval as a true ellipse, which covers π/4, about 0.785, of the rectangle it fits in. Hayward's quick start guide multiplies length × width × depth by 6.7 for an oval where it uses 7.5 for a rectangle, which is 0.893 of the rectangle: to the three figures Hayward prints, what an oval with straight sides and half-circle ends covers when it is twice as long as it is wide, the common above-ground pool. Hayward does not say which oval it means. Choose the shape that matches the pool rather than the factor; a straight-sided oval worked as an ellipse comes out about an eighth short at that proportion.
How do I measure a kidney-shaped pool?: Three measurements: the overall length from the end of one lobe to the end of the other, and the width straight across each lobe at its widest, square to that length. The handbook's formula takes the water surface as 0.45 times Width A plus Width B, times the Length, and refers to a figure for where they are measured that is not reproduced here; the page uses their usual reading, the widths across the two lobes. A lobe wider than the length is flagged, since the length is the longest dimension. That factor is a rule of thumb for the usual kidney outline rather than a property of every kidney, so a pool with a deep waist or unusually full lobes can be noticeably different; where the dose has to be right, a meter on the fill tells you the real figure.
How do I handle a pool with a sloped bottom?: Choose the sloping floor and enter the water depth at the shallow end wall and at the deep end wall; the page works the volume at their average, the way the operator handbook does, and gives that answer at medium confidence. That is exact when the floor falls evenly from one end wall to the other. On the usual pool, a long flat shallow area and a short deep hopper, the plain average overstates the water: split the pool into a shallow section and a deep section, work each at its own depth, and add them.
How many US gallons are in a cubic foot?: Exactly 1,728 ÷ 231 = 7.4805, because a cubic foot is 1,728 cubic inches and a US gallon is defined as 231, and that is the figure this page multiplies by. The handbook and many quick charts round it to 7.5, which reads about a quarter of a per cent high. Until version 1.1.0 this page used 7.48, which read 0.007% low and printed a 10 by 5 m (32.8 by 16.4 ft) pool 1.5 m (4.9 ft) deep, 75 cubic metres, as 74,990 litres (19,811 US gallons); it now reads 75,000 litres (19,813 US gallons).

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.