05/30/2026
Ever wonder how much is enough? Or too much or too little? At least when it comes to worm casting (worm p**p). Well, me too! After a little effort I put together this little guide to hopefully help you decide how much is just right for your needs.
This is very dependent on your gardening needs and can change on what you're using it for. 10–20% by volume for soil, 1–2 tbsp per 6-inch pot for top dressing, and 15–20 lbs. per 100 sq ft for beds are safe starting points for most gardening situations.
Here are the key numbers:
• 1 cubic foot = 7.48 gallons
• 1 gallon = 0.134 cubic feet
• 1 quart = 0.033 cubic feet
• 2 cubic feet = 14.96 gallons (~15 gallons)
Now I recommend 10–20% worm castings be put into the mix so let's break it down a little.
Let's say you buy a 2 cubic foot bag of soil (~15 gallons total):
10% castings
15 gallons × 0.10 = 1.5 gallons castings
Equivalent:
• 1 gallon + 2 quarts
20% castings
15 gallons × 0.20 = 3 gallons castings
Equivalent:
• 3-gallon containers
For a 2 cubic foot soil bag:
• Light feeding → 1.5 gallons castings
• Heavy feeding / demanding crops → 3 gallons castings
Here is a quick Soil Shift cheat sheet I like to use:
Soil Amount 10% Castings 20% Castings
1 cubic foot soil 0.75 gal 1.5 gal
2 cubic feet soil 1.5 gal 3 gal
5 gallons potting mix 2 quarts 1 gallon
10 gallons mix 1 gallon 2 gallons
I hope this helps you all in your future gardening needs.
