Pot Substrate Liters

Substrate Volume Per Pot

For a cylindrical pot, the geometric volume comes from V = π · r² · h, where r is the radius and h is the internal height in centimeters. Divide by 1000 to turn cm³ into liters. Leave roughly 5% of the top empty so irrigation water has somewhere to sit before it soaks in. Skip that gap and the substrate washes over the rim.

Commercial substrates usually run a bulk density of 0.5–0.7 g/cm³, which puts a 5 L pot at about 2.5–3.5 kg of mix. You'll find peat (turfa) in there for water retention, pine bark (casca de pinus) for structure, vermiculite for cation exchange, perlite for drainage and aeration. In tropical blends, coconut coir tends to stand in for the peat.

Applications

Work out how much to buy for a batch of transplants, figure refills for ornamentals, plan the loading on a green roof, or compare brands by the liter instead of by bag weight.

FAQ

Does the pot shape matter? It does. Tapered (frustum-shaped) pots use V = (πh/3)(R² + R·r + r²), and rectangular planters are just length × width × height.

Should I add drainage gravel? Modern horticulture says no. A gravel layer actually raises the perched water table. Go with a uniform, well-aerated substrate and a drainage hole that stays open.

How much does substrate compact? Keep 5–10% extra on hand to top up after the first few waterings, once the peat and bark have settled into their working density.