How to Measure Plant Pots (Complete Guide)

How to Measure Plant Pots Picture Ilustration

Are you potting your favorite plants indoors or outdoors? If so, it will be best to know how to measure plant pots. Why so? Well, each plant type has a unique root system and growth rate.

Therefore, it would be helpful if you knew the pot diameter and volume capacity. Otherwise, most plants become rootbound in small flower pots. And because of that, your plants won’t grow to their best.

Further, you’ll need the pot’s height and diameter to measure its volume elsewhere. Finally, continue reading to learn how to measure your pot’s size and soil depth. 

How to Measure Plant Pots

To measure plant pots, hold a ruler on one end of the pot and move it through the other side to the widest point for round-shaped pots. If your planter pot is square or rectangular, measure the length and width. The depth is measured from the bottom to the top.

Plant Pot Size Guide

How are Plant Pots commonly Sized?

Most measure plant pot sizes in two primary ways; by volume or diameter. The diameter shows the widest point of the pot at the top. That’s a relatively straightforward measurement. 

Even better, you can measure it similarly, no matter the pot’s shape or size. 

Sometimes, one can measure its volume or how enough room it has. That involves doing a few basic calculations. Moreover, you’ll need the following to work out your round pot’s volume:

  • Diameter
  • Depth

But you’ll need the following to measure your square or rectangular pot’s volume:

  • Width
  • Height
  • Length

How to Work Out the Diameter of Different Plant Pot sizes

You’ve undoubtedly seen instructions directing you to use a 12-inch or even 10-inch pot. Well, those measurements always refer to the pot’s diameter. In that case, working out its diameter is straightforward.

Here’s how:

  • Place a tape measure or ruler across the pot’s top rim at its widest part/point. 
  • The measurements of the pot’s one side to the other is the diameter.

Measuring your pot’s diameter is straightforward. However, you’ll need to work out some extra calculations. Doing so will help you work out the pot’s volume.

How to Measure the Volume of a Round size Pot

You’ll need the round pot’s height and diameter to calculate its volume. So, here’s how to work out the pot’s volume:

  • Measure the round pot’s diameter.
  • Measure the round pot’s height.
  • Use the below formula for you to work out the pot’s volume:
  • Height x Pi x Radius2. (where Radius = the diameter’s half and Pi = 3.14).

Here’s an example:

Say we’ve got a round pot with the following measurements

  • A 10-inch diameter.
  • A radius of five.
  • A 15-inch height. 

One can use a formula: 15 x 3.14 x 25 = 15 x 3.14 x 52 = 1177.5 cubic inches.

Then, as we know, one gallon represents 231 cubic inches. Thus, dividing (1177.5 cubic inches) by 231 will help us get the gallon amount:

1177.5 / 231 = 5 gallons, an approximate.

Also, if you’d like to get the volume measurement in liters, multiply the gallon amount by 3.8. In our case, that’ll be 5 x 3.8 = 19 L.

How to Measure the Volume of a Rectangular Pot

When you’ve got a rectangular planter, for instance, one that’s square-shaped at the top with a taller height, use a different formula:

  • Length x Width x Height

So, for this instance, take your tape measure or ruler and measure the pot’s length. Also, estimate the pot’s depth or height and width when doing that. For this, let’s use a square pot as an example. 

The square pot is 6 inches, while the depth or height is 10 inches. Thus, our formula is:

(6 x 6 x 10) = 360 cubic inches (or close to six liters or 1.5 gallons)

When doing this calculation, generally, we round down or up to make it easier.

Here’s another straightforward, but on this, it’s a rectangular pot instead. Moreover, it would help to note that this pot isn’t square. This pot has a 15-inch length, 6-inch width, and 15-inch height. Here’s the formula:

(15 x 6 x 15) = 1350 cubic inches (about 22 liters or almost six gallons).

You can notice the volume has a big difference depending on the pot’s actual measurement. Fortunately, one can see that by looking at the above results.

How Do You Select the Correct Size Pot for Your Plant?

  • A tall pot isn’t necessary for shallow-rooted vegetables like spinach and lettuce. Just pick a diameter that’ll give you growing space for your crops.
  • You’ll need an extra tall planter for root vegetables like beetroot and carrots. Consider the carrots’ average growth and pick a planter of similar height. It would help to remember that beetroots grow in width. So, getting a beetroot pot that’s both deep and wide will be best. 
  • Fruit trees growing in pots need adequate depth. Otherwise, they won’t develop a good and strong root system. The tree’s roots need to supply it with enough nutrients and moisture it needs. Thus, they’ll need a plant pot with adequate depth for their roots to grow freely.
  • Using a pot roughly 1-2 inches deeper than the plant’s current rootball is a general rule. But that’s if you’re growing shrubs or flower plants in pots. Also, this rule applies to the pot’s width. That’ll let your plant continue growing in its new planter.
  • Besides vegetables, you should repot plants in pots for at least a couple of years. Again, like before, pick a plant pot that’s around 1-2 inches larger than the old one. That’ll let your plant put on an extra-lush growth. Thus, keeping its roots healthy.

Quick Guide to Some Standard Pot Sizes (Table)

Here’s a quick guide to standard pot sizes for nurseries. It’ll help your pick a plant pot that’s of a suitable size.

Pot DiameterPot VolumeSuitable Plants
4-inch pot0.125 gallonsSeedlings
5- to 6-inch pot0.25 gallonsSmall succulents
7- to 8-inch pot1 gallonLarger succulents/annuals
10-inch pot3 gallonHerbs or annuals
12-inch pot5 gallonLettuce, strawberries, spinach
14-inch pot7 gallonLarger growing herbs/annuals
16-inch pot10 gallonSmall shrubs
18-inch pot15 gallonLarger vegetables like tomatoes
24-inch pot25 gallonDwarf fruit trees/medium shrubs
30-inch pot30 gallonFruit trees/taller growing shrubs

Remember the above are standard guidelines since the pot’s height and shape may affect its volume. Also, the two may affect the available soil amounts to the plant’s roots. 

Further, these standard sizes may vary among manufacturers.

Rules of Thumb for Measuring Plant Pots

Make sure the plant pot is big enough to drain properly

Also, drainage holes play a critical role in plants’ health. So, ensure your plant pots have them. Moreover, without proper drainage, you may overwater your favorite plants.

In matters of repotting, one should re-home their houseplants every two to four years. Remember, the planter should be 5-10 cm larger. To be sure, check with a local gardening or nursery center. 

When you do so, you’ll get some crucial repotting advice when buying your plants.

Measure your space

There’s nothing worse than buying a pot and realizing it won’t fit within your space. To avoid such, always measure your interior or garden dimensions. Doing that ensures you get a plant container that’ll fit your area. 

Apart from that, consider your plant’s full-grown height and width. Also, ensure you get the tight-fit measurements using a tape measure. 

Generally, pots have small lips that add a few centimeters to their length. Further, your indoor pots may need saucers to harvest excess water. But that’s if you go for drainage holes.

Different Size Pots

How to Measure Plant Pots Image

Small pots

These pots are usually less than 30 cm in diameter and 10 L in volume. So, you have to consider shallow pot plants. The good thing is these sizes make perfect planters for tables and desks. Moreover, this pot size will suit most house plants well. And that’s whether:

  • You plan on brightening up your reception desk using a tiny succulent garden.
  • Or add some poinsettias to your favorite lobby during the festive season.

Medium pots

These pot types are better suited to be floor planters. They measure 30-40 cm in diameter and 10-30 liters in volume. Moreover, those measurements vary among manufacturers. 

They’ll look pleasing within the corners of your office, an office that needs a green splash. Further, one can create a room/space divider using several medium-sized pots. By arranging them together, you can achieve that.

Large pots

At more than a 30-liter capacity and a 40-cm diameter, these pots are made for the following:

  • Large plants whose roots need wide spaces.
  • Trees whose roots need wide spaces.

The roots will only grow and spread out over time if there’s enough growing space. Moreover, these large pots function best within the following:

  • An outdoor setting.
  • A large or open lobby.

Custom pots

If finding a plant pot that best fits your houseplants is challenging, pick a custom planter. They’re available everywhere. And with them, you can develop your dream landscape. 

There are uncountable reasons why custom pots would ideally suit anyone’s needs:

  • You may have got a space/room with specific dimensions.
  • Or you’ve got a houseplant that needs a certain soil depth to grow well.

Well, custom pots stand out among the rest and can take any landscape to a different level. And that’s no matter the reason.

What are Trade Gallons? 

Trade gallons are volume units for standard plant pots in horticultural industries. Moreover, a single trade gallon equals 2.8 L (0.75 US gallons) or three US liquid quarts. 

Some sources note that a single trade gallon equals 2.7 L or 0.71 US gallons.

I recommend a single-gallon pot if we were to go by the volume of the potting soil. So:

  • Should you pick a one-labeled gallon pot in nurseries that hold only 0.664-gallon potting soil?
  • Or, should you choose a plant container you can fit within a (whole gallon) of soil?

Work out the difference between a trade gallon and the regular gallon to solve that challenging factor. Use the following gallon formula:

  • 1 trade gallon = 0.71 regular gallon


Picking plant pots of the correct sizes has always been essential. And that’s whether:

  • You plan to add some greenery to your hotel desk.
  • Or you plan to decorate your office campus with flowers and trees.

Not doing so endangers your plant’s life. Also, it means unnecessary repotting costs will burden you sooner or later. Even better, picking plants that thrive well in pots is advantageous. That’s so since plant maintenance becomes straightforward.

Finally, that was how to measure plant pots. 

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