How to measure a plant pot

Measure the diameter at the widest point of the pot — usually the rim. Measure rim to rim across the top in a straight line through the center. This gives you the diameter, which is the number used in all pot size descriptions. A 10 inch pot measures 10 inches rim to rim. What the label gives you is the outside rim measurement. What the plant cares about is the inside measurement at soil level, which is different. Knowing both is what separates a pot that fits from a pot that doesn’t.

Pot diameter is the measurement across the top rim — the width. Pot depth is the measurement from the rim straight down to the drainage hole — the height of the interior. Both matter, but they matter for different reasons. Diameter determines whether the plant’s root ball fits. Depth determines whether the taproot or lower root structure has room to grow downward. Most standard nursery containers are roughly as deep as they are wide. Most decorative pots are proportionally shallower. If a plant has deep taproots, depth matters as much as width.

Match the pot to the current size of the plant’s root ball, not to the size you want the plant to reach. For a direct repot, the new pot should be one to two inches wider in diameter than the current container. For a pot-in-pot setup where the growers pot sits inside a decorative ceramic, the ceramic needs to be at least as wide as the outer diameter of the growers pot, with a small margin for drainage. A plant moved into a pot much larger than its root system will sit in excess moist soil that the roots cannot access. We have seen this go wrong with considerable frequency over twenty-five years.

The number of people who have bought the wrong size pot with complete confidence is staggering. Not because they did not measure. Because they measured the wrong thing. The outside of a pot and the inside of a pot are two different numbers and only one of them matters to the plant. If your plant does not fit, you measured the outside of the growers pot and the outside of the ceramic pot and compared them. They may match. The inside measurements will be smaller, and those are the ones that determine fit.

Measuring the outside diameter of the growers pot and the outside diameter of the decorative pot and concluding they are the same size. They may be the same number. That number describes different things on the two pots. One is the structural outside of a thin-walled plastic container. The other is the decorative outside of a ceramic pot with walls that have actual mass. The inside of the ceramic pot is meaningfully smaller than the number on the label. We have been making pots for twenty-five years. We have explained this in some form thousands of times. We will explain it again.

Use your palm. The average adult palm is approximately four inches wide. Two palms across the rim is eight inches. Two and a half is ten. It is not precise, but it is accurate enough to rule out a pot that is clearly wrong and confirm that a pot is approximately right. For anything where the fit needs to be exact — particularly when moving a plant from a specific growers pot into a specific ceramic pot with drainage — use a ruler or measuring tape. The approximation works for browsing. The ruler works for buying.

The Minute starts at 3 inch and goes up through the range for smaller plants, herbs, compact tropicals, and anything growing in a standard pint or quart nursery container. The Virago covers the mid to large range — 1 gallon through 3 gallon nursery containers — and has sold over 250,000 units, which is the kind of number that suggests the sizing is right. Both are inside measurements at the soil line. Both have drainage holes that function. The full range with sizes and dimensions is at chive.com/collections/plant-pots.

Yes, if the pot tapers significantly from rim to base. A pot with steep sides — almost straight up and down — has an inside diameter at the soil line close to the rim diameter. A pot that tapers aggressively from a wide rim to a narrow base has considerably less interior space at soil level than the rim measurement suggests. Chive pots use a moderate taper. The inside soil-line diameter is consistently close to the labelled size. When in doubt with any pot from any maker, measure the inside at the depth where the roots will sit, not just the rim.