Tapered Pots: Top Diameter Alone Does Not Describe the Fill Volume; illustrative quantitative diagram
Define the quantity before calculating
A tapered round container has a smaller lower cross-section than its upper opening. Using only the top diameter as though the pot were a cylinder can overstate the volume. Use internal diameters and the actual fill height, not the outside rim dimensions.
Use Potting Soil Calculator with the units and the basis stated on its form. Check what each input represents before carrying the output into another record.
Read the model explicitly
Frustum fill L = π × height × (top² + top×bottom + bottom²) / 12,000. Total = one-pot fill × count.
The Gardening and crops calculators group sits within Biology calculators. Keep a measured observation distinguishable from a hypothetical input when moving between its tools.
A worked unit check
| Input as labeled on the tool | Illustrative value |
|---|---|
| Internal top diameter at fill line (cm) | 30 |
| Internal bottom diameter (cm) | 20 |
| Usable fill height (cm) | 25 |
| Number of matching pots | 4 |
| Labeled bag volume (L) | 40 |
| Output from the illustrative inputs | Value | Unit |
|---|---|---|
| Tapered-pot volume | 12.4355 | L per pot |
| Total geometric fill | 49.7419 | L |
| Whole bags at entered volume | 2 | bags |
Record the original input and its unit with this result. Recalculate when the measurement basis changes; changing a unit label after calculation does not convert the quantity. More decimal places do not remove sampling or measurement uncertainty.
A related quantity
Soil Calculator addresses a related part of the task. Check its own input definition before carrying a number across.
Continue with Potting-Mix Bags: Deduct Existing Roots and Unfilled Space on a Consistent Basis for the other part of this measurement question.
Return to GreenCalc for other subjects. Keep raw observations, chosen assumptions and calculated quantities identifiable so a later revision does not overwrite the basis of the original record.
By GreenCalc · Updated 2026-11-06