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Tank & Cylinder Volume Calculator

With diameter 6 ft, height or depth 4 ft, filled to 100 percent, tank & cylinder volume comes to 846.0 gal — volume. It is reached in 8 steps, the last of which is 113.09734 * 7.48052, and each one is printed on the page with its numbers filled in. The formula is the one published by NIST Handbook 44, not an approximation fitted to it.

Volume of a cylinder in cubic feet, US gallons and liters — round tanks, pools, culverts and post holes.

Formula and sources checked · How we check

Diameter 6 ft, Height or depth 4 ft, Filled to 100

846.0 gal

Volume for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.

It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.

Volume
846.0 gal
3,202.6 liters
Full volume
pi * pow(3, 2) * 4113.097 cu ft
Volume at the fill level
113.09734 * 100 / 100113.097 cu ft
US gallons
113.09734 * 7.48052846.027 gal
Liters
846.02688 * 3.78541183,202.56 L
Curved side area
2 * pi * 3 * 475.398 sq ft
One flat end
pi * pow(3, 2)28.274 sq ft
Total surface area
75.398224 + 2 * 28.274334131.947 sq ft
Weight of that water
846.02688 * 8.347,055.864 lbs

Several at once

A job is rarely one of anything. Work out the first, add it, change the figures and add the next — the list keeps what each line was, and totals them.

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Worked example

A 6 ft round pool filled 4 ft deep holds 113.1 cu ft — 846 US gallons weighing 7,056 lb. That weight is why above-ground pools need level, compacted ground: three and a half tons on an uneven base will find the low corner.

How to work it out yourself

  1. 1.Measure the inside diameter, not the outside. On a steel tank the wall is thin enough to ignore; on a concrete or plastic one it is not.
  2. 2.Height is the vertical dimension of the cylinder and the fill percentage is how much of that height the liquid occupies. For a tank lying on its side this formula does not apply.
  3. 3.The weight line is for water at about 8.34 lb per gallon. Fuel is lighter and most solutions are heavier, so scale it by density if the contents are not water.

The formula

  1. Full volumepi * pow(3, 2) * 4
  2. Volume at the fill level113.09734 * 100 / 100
  3. US gallons113.09734 * 7.48052
  4. Liters846.02688 * 3.7854118
  5. Curved side area2 * pi * 3 * 4
  6. One flat endpi * pow(3, 2)
  7. Total surface area75.398224 + 2 * 28.274334
  8. Weight of that water846.02688 * 8.34

Source: NIST Handbook 44 — liquid measuring devices, Wolfram MathWorld — cylinder

Questions people actually ask

Why 7.48 gallons per cubic foot?
A US gallon is defined as 231 cubic inches, and a cubic foot is 1,728 — the ratio is 7.48052. The imperial gallon is larger, at 6.229 per cubic foot, so British tank figures do not transfer.
Does this work for a tank lying on its side?
Only when it is completely full or completely empty. A partly filled horizontal cylinder needs the circular-segment formula, because the surface area of the liquid changes with depth.
How heavy is the water?
8.34 lb per US gallon at room temperature, or 62.4 lb per cubic foot. Multiply before you put a tank on a deck or a mezzanine — water is one of the densest things people move casually.

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