Tank Volume Calculator
This tank volume calculator finds the capacity of a tank from its shape and dimensions, in liters, cubic meters, and gallons. Enter the size and the tank volume calculator returns the full volume and, for a horizontal cylinder, the partial volume at any fill depth. It works as a tank size calculator for cylindrical, rectangular, and round tanks, so you can size storage or read how much is left.
Results
The Tank Volume Calculator is part of our Fluids collection. Browse more fluids to size, convert, and check your work alongside this tool.
What the tank volume calculator does
Whether you are sizing a new tank or checking how much a full one holds, the tank volume calculator turns dimensions into capacity. As a tank size calculator it covers the common shapes: a cylinder standing or lying down, a rectangular box, and a round tank. Enter the measurements and the calculator for tank volume reports the result in liters, cubic meters, and gallons, so a water tank calculator answer works whether your supplier talks in litres or gallons.
The tank volume formula by shape
A vertical cylinder or round tank uses the cylinder volume:
A rectangular tank is simply length times width times height:
A horizontal cylinder partly full is harder, because the liquid forms a circular segment; the tank volume calculator integrates that segment so the round tank volume calculator gives the right partial figure. In every case the calculator for tank volume converts the raw cubic measure into liters and gallons for you.
Tank volume calculator example
A vertical cylindrical water tank 1.2 m in diameter and 2 m tall, using the tank volume formula:
That is about 598 US gallons. Enter the diameter and height and the water tank volume calculator returns all three units at once.
How to use the tank volume calculator
Pick the tank shape, then enter the dimensions it asks for: diameter and length for a cylinder, or length, width, and height for a box. The tank volume calculator computes the full capacity and shows it in three units. For a horizontal cylinder it also accepts a fill depth, so the water tank capacity calculator can tell you the volume of liquid held in the tank, not just the maximum.
Reading the tank volume calculator result
The full volume is the tank capacity; the partial volume is how much is in it now. Remember that a tank is rarely filled to the brim, so for usable storage subtract an air gap at the top. When sizing a water tank calculator result against demand, match the capacity to your daily use and refill rate rather than the theoretical maximum. The gallons figure from the tank gallon calculator is handy for pumps and fittings rated in gallons per minute.
When to use the tank volume calculator
- Sizing rainwater or storage with the water tank capacity calculator
- Reading how full a horizontal tank is with the round tank volume calculator
- Planning fuel or chemical storage with the calculator for tank volume
- Converting a rectangular tank volume to liters and gallons
Common tank volume calculator mistakes
- Outside dimensions. Capacity uses the internal size; the calculator for tank volume overstates if you measure the shell.
- Assuming linear fill. A horizontal tank needs the round tank volume calculator, since depth and volume are not proportional.
- Filling to the brim. Leave an air gap; usable capacity is below the tank size calculator maximum.
Tips for accurate results
- Measure internal dimensions for the tank volume calculator, not the outer shell.
- For horizontal tanks, use the fill depth so the round tank volume calculator gives the real contents.
- Subtract a top air gap when sizing usable storage.
Getting the tank size calculator inputs right
The tank volume calculator is only as accurate as the dimensions you give it, and the usual trap is inside versus outside measurement. Capacity depends on the internal dimensions, so a tank measured across its outer shell overstates the volume by the wall thickness, which matters for thick plastic or insulated tanks. For a cylinder, the radius is squared in the formula, so a small error in diameter grows into a larger error in volume; measure the bore carefully. When a manufacturer quotes a nominal size, treat it as a label rather than a precise figure and confirm with the calculator for tank volume if the exact capacity matters.
Partial volume and the round tank volume calculator
Reading how much is left in a horizontal cylinder is where a round tank volume calculator earns its place. Because the tank lies on its side, the liquid surface is a chord across a circle, and the volume does not rise evenly with depth: the tank fills slowly at the bottom, quickly through the middle, and slowly again near the top. A dipstick reading of half the diameter is exactly half full, but a quarter of the diameter is far less than a quarter full. The water tank capacity calculator handles this segment math so a depth measurement turns into a trustworthy volume, which is what makes it useful for fuel and chemical tanks where a wrong reading is costly.
Tank volume calculator chart
Capacity of a vertical cylindrical tank at common sizes, a quick tank size calculator chart:
| Diameter | Height | Volume (liters) | US gallons |
|---|---|---|---|
| 1.0 m | 1.0 m | 785 | 207 |
| 1.2 m | 2.0 m | 2262 | 598 |
| 1.5 m | 2.0 m | 3534 | 934 |
| 2.0 m | 2.5 m | 7854 | 2075 |
Tank Volume Calculator FAQ
How do I calculate tank volume?
Multiply the cross-section area by the length or height. The tank volume calculator uses π × r² × h for cylinders and L × W × H for boxes, then converts the calculator for tank volume result to liters and gallons.
Can it do a partly full horizontal tank?
Yes. Enter the fill depth and the round tank volume calculator works out the circular segment of liquid, so the water tank capacity calculator reports the actual contents, not just the maximum.
Does it handle rectangular tanks?
It does. Select the box shape and enter length, width, and height, and the tank size calculator returns the rectangular tank volume in liters, cubic meters, and gallons.
Litres or gallons?
Both. The tank volume calculator litres output sits alongside US gallons and cubic meters, so the water tank calculator answer suits whichever unit your equipment uses.