How Much Potting Soil Is Enough?


How many times have you wondered about the amount of potting soil you need to fill a flower pot or how many seeds you can start with one bag of soil?

Here at Geo Growers our Thunderhead Potting Soil comes in a 16 quart bag and a 20 gallon bag. It should be no mystery as to how much you need when it is time to repot existing plants or get your seeds started.cactus

It will be easiest to start small and work up to medium and large volume pots.

Here at Geo Growers we highly recommend our Thunderhead Cactus & Succulent Mix for all of your seed starting needs.  3.5 and 4 inch pots are probably the most common for seed starting.

Pot Size 16 Quart Bag 20 Gallon bag
3.5 inch pot ~76 ~380
4 inch pot ~33 ~165

If you are not interested in seed starting, but want to re-pot an existing plant, here are some standard medium size pots.  Thunderhead Original Potting Mix is great for re-potting a wide variety of houseplants and vegetable.

Pot Size 16 quart bag 20 gallon bag
6 inch pot ~13 ~63
8 inch pot ~5 ~26
10 inch pot ~3 ~16
12 inch pot ~1 ~6


So a quick look tells you that a 16 quart bag of Thunderhead Potting Soil will fill IMG_2748approximately 13 six inch pots, 5 eight inch pots, 3 ten inch pots, or 1 twelve inch pot.

Larger pots are a bit easier to figure out since they are not fractions of a quart, but this should help as well.

Pot Size Volume
8 inch pot 3 quarts
10 inch pot 5 quarts
12 inch pot 12 quarts
14 inch pot 18 quarts
16 inch pot 22 quarts
20 inch pot 28 quarts
24 inch pot 36 quarts

For larger volumes it is good to know that 1 US quart = 0.033420139 cubic foot.  That should help you figure out how much potting soil you may need for larger planters or pots.

The examples above are “typical” pot volumes, and some designs may vary considerably.

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