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Planter Soil Volume Calculator

Enter the inside width, depth and height of a rectangular planter plus the water space, and instantly get the liters of potting soil needed, the total for several planters, and how many store-bought soil bags to buy.

Input

Enter the inside dimensions of a rectangular planter box and this tool calculates how much potting soil (in liters) you need for planting. Soil is normally not filled to the rim — a 'water space' is left at the top to hold water when you water the plants. Use the result as a rough guide only.

cm
cm
cm
cm
pcs
Store soil bag size

Result

Soil needed (total for 1)

19.2L

With 14.0 L soil bags, about2 bagsis a good guide

Filled to rim (each)

21.6 L

After water space (each)

19.2 L

Total (for 1)

19.2 L

Bags needed by store soil bag size

Bag sizeBags for the amount neededBuy guide (rounded up)
5Labout 3.84 bags4 bags
10Labout 1.92 bags2 bags
14L (selected)about 1.37 bags2 bags
20Labout 0.96 bags1 bags
25Labout 0.77 bags1 bags
40Labout 0.48 bags1 bags

Usable soil depth: 16.0 cm (height minus the water space)

How it works

  • Measure and enter the inside dimensions (the inner width, depth and height where soil goes), not the outside dimensions. Using outside measurements overstates the volume.
  • Volume (L) is calculated as width (cm) x depth (cm) x (height - water space) (cm) / 1000. The water space is the gap left below the rim to hold water when watering, usually about 1-3 cm of the height.
  • 'Filled to rim' is the volume if soil is added without leaving a water space; 'after water space' is the actual amount of soil you need. Enter a quantity to get the combined volume for several planters.
  • Pick a store soil bag size to see how many bags the required amount works out to and the rounded-up number of bags to buy. Soil settles and shrinks over time, so it is safer to have a little extra.
  • Round planters, pots that taper toward the bottom, and the use of drainage stones change the actual amount needed. Treat this tool's result as a rough guide only.