How to measure plant pot size at home?

Use a ruler or tape to measure the inside width across the top opening. Round to the nearest common size in cm or inches.

What size pot should I choose when repotting?

A safe approach is to size up one step at a time, typically 2–5 cm (about 1–2 inches) wider than the current pot.

Why do pots with the same litre label vary in size?

Different manufacturers use slightly different shapes and heights. Use litre labels to shortlist, then confirm exact planter dimensions if precision matters.

Does pot shape and depth matter?

Depth can affect watering forgiveness. Taller pots often manage moisture better than very shallow pots, especially if drainage is not ideal.

Plant Pot Size Guide: How to Measure Pots and Choose the Right Size

Q: How are plant pots measured?

Most pots are measured by the inside top diameter across the rim. Some listings also use litres to describe soil capacity.

Pot sizing should be simple—until you see inches, centimeters, litres, and nursery labels like “P9” on the same shelf. This fast, practical plant pot size guide shows how pots are measured, how to compare standard sizes, and what size to choose for houseplants, herbs, and vegetables.

What Pot Size Means: Diameter vs. Litres

In many countries, “pot size” usually means the pot diameter at the top opening. A “6-inch pot” is roughly 6 inches across the rim.

In garden trade and nursery contexts, you will also see pot sizing by volume, most commonly in litres (for example, 2L, 5L, 10L). Both systems are common, so the key is to identify whether a listing is talking about diameter or capacity.

Diagram showing how to measure pot top diameter and height

How Are Plant Pots Measured?

Diameter measurement

Measure the inside width across the top rim.
Round to a standard size (for example, 15 cm, 20 cm, 25 cm; or 6 inch, 8 inch, 10 inch).

Volume measurement

If a pot is listed as 2L, 5L, or 10L, the number refers to soil capacity.
Two pots with the same litre label can still differ slightly by brand, so treat charts as practical guidance.

Standard Pot Sizes: Quick Reference Chart

Below is a simple pot size chart to help you translate common litre labels into typical top diameters. Use it as a quick guide when comparing planter sizes across suppliers.

Common label	Typical top diameter	Best for
P9 nursery pot	9 cm, about 3.5 in	Young plants, herbs, starter stock
1 litre	13 cm, about 5 in	Small houseplants, herbs
2 litre	17 cm, about 6.5 in	Compact shrubs, faster growth than 1L
3 litre	19 cm, about 7.5 in	Bushier plants, stronger root space
5 litre	22.5 cm, about 9 in	Larger shrubs, patio planters
10 litre	28 cm, about 11 in	Specimen plants, mixed patio planting
20 litre	35.5 cm, about 14 in	Mature shrubs, feature planting
40 litre	50 cm, about 20 in	Large statement planters

Tip: If you are comparing planter dimensions for shipping, always confirm the outer diameter and height in the supplier spec sheet. Charts help you shortlist, specs confirm the final choice.

Repotting a houseplant from a smaller nursery pot into a one-step larger pot

What Size Pot Should I Choose?

For repotting houseplants

A reliable rule is to move up one step at a time. For example:

From a 10 cm or 4 in nursery pot → choose around 15 cm or 6 in
From a 15 cm or 6 in → choose around 20 cm or 8 in

This avoids the two most common mistakes: a pot that is too small and dries out fast, or a pot that is too large and stays wet too long.

For herbs and vegetables: minimum pot diameter

If your reader is asking what size pot they need, edibles are the fastest way to answer. Use the table below as a baseline for one plant per container unless noted.

Minimum pot diameter	Examples
10 in	Small herbs, strawberry
14 in	Most herbs, cabbage, collards, spinach (3–4), non-heading lettuce (3–4), arugula (3)
18 in	Broccoli, cauliflower, large cabbage, small eggplant, small pepper, determinate tomato
24 in	Large pepper, summer squash, indeterminate tomato, cucumber, artichoke, mixed combinations

Pot Shape and Depth: Simple Rules That Actually Help

Most of the time, plant pot sizes matter more than shape. But depth can change how forgiving a pot is.

Taller pots are usually safer for watering because roots are farther from the consistently wetter zone at the bottom of the container.
Very shallow pots dry out faster at the top, but can stay wet at the bottom if drainage is poor.
When in doubt, choose a pot with drainage holes and a moderate depth rather than an extra-wide, shallow bowl.

Comparison of tall vs. shallow pots and how depth impacts root moisture

Close-up of drainage holes on the bottom of a plastic plant pot

Drainage and Material Notes

Drainage is non-negotiable. Regardless of flower pot sizes or flower pot dimensions, the container should support consistent watering and airflow.

Choose pots with drainage holes whenever possible.
Match soil mix to the plant type.
If you are shopping plastic pot sizes for retail, confirm whether the listed size refers to inner top diameter or outer diameter.

If consistent moisture is the goal, consider self-watering pots and planters as a solution. They can reduce watering swings by separating the water reservoir from the root zone.

If You Stock Planters: A Simple Size Assortment

For retailers and garden center buyers, a clean assortment usually outsells a messy wall of random sizes. A practical starting mix:

Small: 9–13 cm for starter plants and impulse buys
Medium: 17–22.5 cm for most indoor plants and patio herbs
Large: 28–35.5 cm for statement plants and outdoor use

Nested planters organized into small, medium, and large size groups for wholesale stocking

FAQs

How to measure plant pot size?

Measure the inside width across the top rim. That top diameter is the most common sizing method for pots and planters.

Are nursery pot sizes the same as decorative pot sizes?

Not always. Nursery pots are often labeled by diameter or trade size. Decorative pots may list diameter, height, or volume depending on the seller.

Does a bigger pot always mean better growth?

Not always. Bigger pots can support growth, but oversizing can keep soil wet too long if the plant is small or drainage is poor.

Why do two pots with the same litre label look different?

Manufacturers vary slightly in shape and height. Use litre labels to shortlist, then confirm exact planter dimensions if you need a precise fit.

What size pot is best for indoor plants?

For most indoor plants, size up gradually. A pot that is one step larger than the current container is usually the safest choice.