How to Measure Plant Pots to Find the Right Size
Selecting the right container goes beyond aesthetics. This guide explains the principles of pot sizing to support your plant's health and ensure a proper fit.
Correctly measuring plant pots removes guesswork when selecting a new plant, repotting, or finding a decorative container. Matching a plant to the right-sized home is important for its long-term well-being. Knowing a pot’s precise dimensions allows for better planning and care.
The Key Measurements
To measure a round pot, you will need a tape measure or ruler. The primary dimension is the top inside diameter. Stretch the tape measure across the widest point of the opening, from one interior edge to the other. To find the widest point, you may need to slide the end of the tape measure back and forth until you find the largest measurement.
Next, determine the pot’s height by placing your ruler inside the container, measuring from the interior base up to the rim. Measuring the inside depth is more accurate than the exterior height, as many pots have feet or raised bottoms that can give a misleading measurement. For square or rectangular planters, you measure the interior length and width of the opening instead of the diameter.
Understanding Pot Sizes
When you purchase a pot from a store, the size listed, such as a “6-inch pot” or “10-inch pot,” refers to the top diameter. This is a standard in the horticulture industry. While these are general categories, the exact measurement may vary slightly, so it is a good idea to measure it yourself if the fit is important.
You may also encounter nursery pots sold by volume, using terms like “#1,” “#3,” or “#5.” These are called “trade gallons,” which are not equivalent to a standard liquid gallon and hold less soil. These volume-based sizes correspond loosely to diameter; for instance, a #1 container is roughly equivalent to a 6 or 7-inch pot, but this can differ between growers.
Applying Your Measurements
A primary reason to measure a pot is for repotting. A guideline is to choose a new pot that is 1 to 2 inches larger in diameter than the plant’s current container. This provides enough fresh soil and space for roots to expand without overwhelming the plant in an overly large pot, which can cause the soil to stay too wet and harm the roots.
These measurements are also useful when selecting a decorative pot, called a cachepot, which does not have drainage holes. The decorative pot’s opening must be slightly larger than the diameter of the plastic nursery pot you intend to place inside. The cachepot’s internal height should be enough to hold the nursery pot so its rim sits at or just below the decorative pot’s edge.