Potting Soil Calculator
Find how much potting mix fills your containers — in quarts, cubic feet and bags — for round or rectangular pots.
How it works
Round: volume(in³) = π × (d ÷ 2)² × depth · Rectangular: volume(in³) = length × width × depth · Quarts = in³ ÷ 57.75 · Cubic feet = in³ ÷ 1728
A pot’s soil volume is the geometry of its interior: a cylinder for round pots (π r² × depth) or a box for rectangular planters (length × width × depth). Bagged potting mix is usually sold in dry quarts, and one US dry quart is 57.75 cubic inches, so dividing the volume by 57.75 converts to bag units. Buy a little extra, since mix settles and compresses after watering.
Worked example
A 12-inch-diameter pot 10 inches deep: π × 6² × 10 = 1,131 in³. In quarts that is 1131 ÷ 57.75 = 19.6 qt (0.65 ft³). At 16 qt per bag, you need ⌈19.6 ÷ 16⌉ = 2 bags.
Frequently asked questions
How many quarts of soil for a pot?
It depends on the pot’s volume. As a guide, a 10-inch pot holds about 6–7 quarts, a 12-inch about 15–20 quarts, and a 14-inch about 25 quarts — but measuring your exact dimensions is far more accurate.
Why quarts instead of cubic feet?
Retail potting mix for containers is almost always labeled in dry quarts, while bulk garden soil is sold in cubic feet or yards. This calculator gives both so you can match whatever the bag shows.
Should I fill the pot completely?
Leave about an inch of headspace below the rim so water can pool and soak in rather than running off. This calculator uses your entered depth, so subtract the headspace from the pot’s full depth if you want to be precise.
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This calculator is for educational purposes. Double-check important results before acting on them.