Tank Volume Calculator
Find the capacity of a tank in gallons, liters, cubic feet, and cubic meters from its shape and size. Enter the liquid level to see how much liquid is in the tank, how much space is left, and how full it is. For a swimming pool, use the Pool Volume Calculator.
- Choose US or Metric. You can still change the unit of any single field.
- Choose the Tank shape. A capsule tank is a cylinder with rounded ends, like most propane tanks.
- Enter the dimensions of the tank. For a capsule tank, the Length or Height is the whole tank from end to end, including the rounded ends.
- Optionally, enter the Liquid level, measured up from the inside bottom of the tank. Leave it blank to see the capacity only.
Fields accept whole numbers, decimals, fractions, and mixed numbers, such
as 48, 10.5, 3/4, or
7 1/2.
How to calculate tank volume
The capacity depends on the shape. For round tanks, the radius is half the diameter:
Vertical cylinder = π × radius² × height
Horizontal cylinder = π × radius² × length
Rectangular = length × width × height
Capsule = π × radius² × (overall length − diameter) + 4 ÷ 3 × π × radius³
A capsule is a cylinder with a half sphere on each end. The two ends make one sphere, so the calculator adds the volume of a sphere to the cylinder between the ends.
To get gallons, divide cubic inches by 231. The calculator uses the US gallon, which is 231 in³ or about 3.785 L, not the imperial gallon. One cubic foot is about 7.48 gallons.
Liquid volume at a given level
In a vertical cylinder or a rectangular tank, the liquid volume grows in step with the level: a tank filled to 3/4 of its height is 75% full. Horizontal and capsule tanks are narrower near the bottom and top, so the volume does not follow the level. For a horizontal cylinder, the liquid fills a slice of the circle, a circular segment, along the length:
Segment area = radius² × acos((radius − level) ÷ radius) − (radius − level) × √(2 × radius × level − level²)
Horizontal cylinder liquid volume = segment area × length
In a horizontal capsule, the segment runs along the straight part, and the rounded ends hold a spherical cap, π × level² × (3 × radius − level) ÷ 3. A vertical capsule fills the bottom half sphere first, then the straight part, then the top half sphere.
For example, a horizontal tank 48 in across that is filled 12 in deep, a quarter of the way up, is only 19.55% full. At 24 in, half the diameter, it's half full.
How to measure a tank
- Use inside measurements if you can. Outside measurements include the walls, so the capacity comes out a little high.
- Measure capsule tanks from end to end. Manufacturers list the overall length, and the line between the straight part and the rounded ends is often hard to see.
- Measure the liquid level from the inside bottom. A dipstick or a marked pole, held straight up, gives the depth of the liquid. The tank should be level.
Manchester Tank lists a 250 gal propane tank as 30 in in outside diameter and 7 ft 10 in overall, with hemispherical heads. As a capsule, those outside measurements give 257.04 gal, about 3% more than the listed water capacity. Some smaller tanks have shallower elliptical heads, and the calculator gives more than they hold. If you aren't sure of the shape of the ends, check the manufacturer's capacity.
Examples
Vertical water tank
A tank 48 in across and 60 in tall holds π × 24² × 60 = about 108,573 in³, or 470.01 gal (1,779.20 L). With the water 45 in deep, it holds 352.51 gal and is 75% full, with 117.50 gal of space left.
Horizontal tank
A horizontal tank 48 in across and 10 ft long holds 940.03 gal. At a level of 12 in, it holds 183.78 gal and is 19.55% full.
Capsule propane tank
A capsule tank 30 in across and 7 ft 10 in overall has a straight part of 94 − 30 = 64 in and holds 257.04 gal. At a level of 10 in, it holds 73.01 gal and is 28.4% full.
Metric dimensions
A vertical tank 1,200 mm across and 1,500 mm tall holds 1,696.46 L. At a level of 900 mm, it holds 1,017.88 L and is 60% full.
FAQ
About 7.48 US gallons. A cubic foot is 1,728 in³, and a US gallon is 231 in³, so 1,728 ÷ 231 = 7.48.
If the gauge shows a percentage of the capacity, multiply the capacity by that percentage. A 470.01 gal tank at 60% holds about 282 gal. If you can measure the depth instead, enter it as the liquid level.
Yes. Choose Rectangular and enter the inside length, width, and height. A tank 48 in long, 13 in wide, and 21 in tall holds about 56.73 gal. Gravel, rocks, and decorations take up some of that space.
A round tank is narrowest at the bottom, so the first part of the height holds less liquid. A horizontal tank 48 in across, filled 12 in deep, is 19.55% full. It's half full at half the diameter.
Related calculators
- Pool Volume Calculator
How many gallons or liters your pool holds, from its shape, size, and shallow and deep end depths.
- Cubic Yard Calculator
Volume in cubic yards from length, width, and depth.
- Square Footage Calculator
Area in square feet, square yards, and square meters.
- Feet and Inches Calculator
Add and subtract feet, inches, and fractions, with the total in feet and inches and decimals.