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Potting Soil Calculator

Container & Soil Inputs

Leave a little space at the top for watering. Enter your actual fill depth when possible.

Only subtract when a separate drainage layer is actually planned.

RESULT

Total Potting Soil Needed0.65 cu ft18.5 liters • 16.8 dry quarts
Per Container0.65cu ft each
Quantity1same-size containers
Total Liters18.5liters

Soil Bag Breakdown

Enter a bag price for an estimated total.

Bag sizes use US dry quarts; check the actual package label.

Pot Cross-Section (Side View)

Round pot

Soil layer and optional headspace are illustrative, not to scale.

Formula & Worked Example

Round: π × (diameter ÷ 2)² × effective fill depth

12 in diameter × 10 in depth → 0.65 cu ft

Conversions: 1 cu ft = 28.3168 L ≈ 25.714 US dry qt.

Frequently Asked Questions

Do I subtract a top fill margin?

Yes, if the plant pot will not be filled to the rim. Subtract the unfilled height from the measured depth.

Should I include a drainage layer?

Only subtract a separate layer from the soil height if you actually intend to install one. Container drainage holes remain essential.

Which bag size should I buy?

Choose the package size sold locally and round up the number of bags. Verify whether the bag is labeled in dry quarts, liters, or cubic feet.

How are tapered pots calculated?

A tapered pot is approximated as a conical frustum. Its diameter decreases linearly with height.

Related Resources

University of Minnesota Extension — Potting houseplants ↗Royal Horticultural Society — Potting composts ↗

Planting recommendations vary by plant species, substrate, and pot drainage.

↗ Biology

Potting Soil Calculator Calculator Calculate the volume of potting soil needed to fill a rectangular planter or round pot. — free online calculator.

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Updated: October 10, 2026