Pot Volume Calculator
Measure the inside of your pot to estimate how much growing medium fits below the fill line.
Estimate the mix volume
Measure the inside of the pot. The result is a geometric estimate, not a bag-count guarantee.
The starting dimensions are examples. Replace them with your pot's inside measurements.
Worked examples using a stated taper
These examples assume the inside bottom is 70% of the top diameter and the height equals the top diameter. They are geometry examples, not manufacturer-standard pot dimensions.
| Inside top diameter | Bottom diameter | Height | Liters | US dry quarts |
|---|---|---|---|---|
| 4 in | 2.8 in | 4 in | 0.60 | 0.55 |
| 6 in | 4.2 in | 6 in | 2.03 | 1.84 |
| 8 in | 5.6 in | 8 in | 4.81 | 4.37 |
| 10 in | 7 in | 10 in | 9.40 | 8.53 |
| 12 in | 8.4 in | 12 in | 16.24 | 14.74 |
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How the estimate works
A round tapered pot is treated as a frustum. A straight-sided pot is a cylinder, and a rectangular planter is a box. For a frustum, V = pi x h / 3 x (R^2 + Rr + r^2), where R is the inside top radius and r is the inside bottom radius. For a partial fill, the tool scales the height and interpolates the radius at the fill line. The result is geometry from your dimensions, not a promise about the bag count: leave room for the root ball, headspace, and settling.
A cylinder uses V = pi x r^2 x h; a rectangular planter uses V = width x length x height. Dimensions are inside measurements in inches. The outputs convert cubic inches to liters and US dry quarts.
Potting media is often labelled in US dry quarts. One US dry quart is about 1.101 liters. The calculator reports both so you can compare a geometric estimate with the package label.
The built-in examples assume a bottom diameter of 70% of the top and a height equal to the top diameter. Those are explicit example assumptions, not measurements of a standard pot. Download all worked examples (CSV).