What this calculator does
This pot volume calculator finds how many litres a cylindrical pot, bucket, planter or similar container holds, from its diameter (or radius) and height. It is the same cylinder-volume formula used for pipes and tanks, applied to a solid container rather than a hollow one, so there is no wall thickness or inner radius to account for.
Most plant pots, buckets and planters are close enough to a true cylinder for this to give a useful estimate, even when the sides taper slightly, since a straight average of the top and bottom radius is usually close enough for potting mix or liquid capacity purposes. For a pot with pronounced tapering, measuring the radius partway up the sides gives a more representative figure than using either the very top or very bottom.
The formula
The volume of a cylinder is π times the radius squared, times the height. Measuring in centimetres gives a volume in cubic centimetres, and dividing that by 1,000 converts it to litres, since one litre is exactly 1,000 cubic centimetres.
| Term | Meaning |
|---|---|
| r | Radius: half the diameter, measured across the widest circular cross-section of the pot. |
| h | Height: the depth of the pot from base to rim, in the same unit as the radius. |
| V | Volume, calculated in cubic centimetres and then converted to litres. |
The inputs explained
| Field | What to enter |
|---|---|
| Enter as | Choose whether the measurement you are entering is the full diameter across the pot, or the radius (half that distance). |
| Diameter or radius (cm) | The diameter or radius of the pot, in centimetres, matching whichever you selected above. |
| Height (depth) (cm) | The height (depth) of the pot, in centimetres, measured from the base to the rim. |
When to use it
Choosing a pot for a plant
Nursery advice is often given in litres, such as "needs at least a 10 litre pot". Measuring a pot on hand with a tape measure and running it through this calculator checks whether it meets that guideline before repotting.
Working out potting mix needed
Bags of potting mix or soil are usually sold by the litre. Knowing a pot's volume in litres, and how many pots need filling, gives a straightforward estimate of how much mix to buy.
Sizing a bucket or container for liquid
The same formula applies to a cylindrical bucket or drum used to hold water, feed or any other liquid, giving its capacity in litres from a tape-measure reading.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How pot volume changes with diameter at a fixed height
A fixed 35 cm height, across a range of pot diameters.
| Diameter | Pot volume |
|---|---|
| 15 cm | 6.19 litres |
| 20 cm | 11.00 litres |
| 25 cm | 17.18 litres |
| 30 cm | 24.74 litres |
| 40 cm | 43.98 litres |
| 50 cm | 68.72 litres |
How pot volume changes with height at a fixed diameter
A fixed 30 cm diameter, across a range of pot heights.
| Height | Pot volume |
|---|---|
| 15 cm | 10.60 litres |
| 20 cm | 14.14 litres |
| 25 cm | 17.67 litres |
| 30 cm | 21.21 litres |
| 40 cm | 28.27 litres |
| 50 cm | 35.34 litres |
Questions
What if my pot is not a perfect cylinder?
Most pots taper slightly from a wider rim to a narrower base, or the reverse. Using the radius measured partway up the sides gives a reasonable average for this calculator, since the true shape is closer to a cone frustum, and the difference is usually small for typical pot proportions.
Does this account for the wall thickness of the pot?
No, this treats the pot as a solid interior space and calculates internal capacity from the measurements you give it. If you measure the outer diameter of a thick-walled pot, the true internal volume will be a little smaller than the result shown.
How is this different from a hollow cylinder or pipe calculator?
A hollow cylinder or pipe calculator works out the volume of material forming a tube wall, using both an outer and an inner radius, which suits pipes and rings. A pot is a solid, single-cavity container, so it only needs one radius and height, which is what this calculator uses.
Can I convert the result to gallons?
Yes, the result includes an approximate US gallons figure alongside litres, calculated using the standard 3.78541 litres per US gallon conversion.
For a container with both an inner and outer wall, such as a pipe or tube, see the hollow cylinder volume calculator.