Tank Volume Calculator
How much a cylindrical, rectangular or capsule tank holds, standing or lying down, and how much is in it at a measured liquid depth.
Result
Buy 564.02 gal
Inside dimensions give what the tank holds; outside ones overstate it.
- Liquid in the tank
- 564.02 gal (75.4 ft³, 2,135.04 L)
- Share of the tank filled
- 100%
- Weight if that liquid is water
- 4,707 lb (2,135 kg)Estimate
https://calcgallery.com/area-volume/tank-volume-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Tank Volume Calculator
- Choose the tank's shape and whether it stands upright or lies on its side.
- Enter its inside dimensions. For a capsule, measure the length end to end, across the rounded ends.
- For a tank that is not full, choose partly filled and enter the depth of liquid, measured with a dipstick from the surface to the bottom.
The shapes
upright cylinder volume = π × (D ÷ 2)² × depthrectangular volume = length × width × depthlying cylinder volume = segment area × lengthsegment area = r² × acos((r − h) ÷ r) − (r − h) × √(2rh − h²)capsule add a spherical cap at each end: π h² (3r − h) ÷ 3For a tank on its side, the liquid’s cross-section is a circular segment: the part of the circle below the liquid line. Its area grows slowly at first, quickly through the middle and slowly again near the top, so a dipstick reading converts to volume through the formula rather than by simple proportion. The capsule adds the two rounded ends, which together make a sphere; at any depth they hold a spherical cap of that height.
Reading the result
The capacity is the tank brim full. The liquid figure and the share filled follow from the depth you measured. Fuel and water tanks are rarely filled to the brim and many have a fill pipe or vent above the top of the shell, so the usable volume on the nameplate can be less than the geometric capacity.
With your numbers
- Volume = area of the circle below the liquid line × straight length, plus the two end caps for a capsule
Quick reference
Inside dimensions give what the tank holds; outside ones overstate it.
| Job | Result |
|---|---|
| Upright cylinder, 4 × 6 ft | Tank capacity: 564.02 gal |
| Lying cylinder, 4 × 10 ft, 1 ft deep | Liquid in the tank: 183.78 gal |
| Lying cylinder, half full | Liquid in the tank: 470.01 gal |
| Rectangular, 4 × 2 × 3 ft | Tank capacity: 179.53 gal |
| Capsule, 1 m × 3 m | Tank capacity: 2,094.4 L |
| Upright capsule, 2 × 6 ft, 0.5 ft deep | Liquid in the tank: 4.9 gal |
| Lying cylinder, 1.2 × 2.5 m | Tank capacity: 2,827.43 L |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
1 source
NIST Chemistry WebBook, water at 4 °C and 0.101325 MPa: 999.9749 kg/m³ (IAPWS-95), https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185, rounded to the conventional 1000 kg/m³ of NIST SP 811 (2008) Appendix B, centimeter of water, conventional = 98.0665 Pa.
Used for
- The conventional density of water, 1000 kg/m³. Pure water at 4 °C, its densest, is 999.97 kg/m³.
Common questions about the Tank Volume Calculator
- Why doesn't depth convert to gallons in proportion in a tank on its side?
- Because a circle is widest in the middle. The first foot of liquid in a 4-foot tank on its side sits in the narrow bottom of the circle and holds under a fifth of the tank; the next foot, through the wide middle, holds almost a third. Only the exact centre line splits the volume in half. An upright tank has straight sides, so there every inch of depth holds the same amount.
- How do I measure a tank that is lying down?
- Measure the inside diameter across the circular end and the length of the straight part. A tank you can only measure from outside is slightly smaller inside by twice the wall thickness each way; for steel that is small, for concrete or thick plastic it matters.
- What is a capsule tank?
- A cylinder with a rounded, hemispherical cap on each end, the shape of many propane and pressure tanks. The page measures it end to end and treats the caps as half spheres of the same diameter. Tanks with flatter, dished ends hold a little less than this, and many state their capacity on the nameplate, which is worth checking first.
- How much does the water in the tank weigh?
- The page multiplies the liquid volume by 1,000 kilograms per cubic metre, about 8.35 pounds a US gallon. Other liquids weigh more or less than water. The page says nothing about whether a floor, stand or roof can carry that weight.