Visit Us In-Store: 2/322 Hobart Rd, Youngtown TAS
Substrate Volume & Cost Calculator
Work out how much growing media your pots need, how many bags to buy and what it costs
Pots
Most pots are sold by volume, such as 11 L or 25 L.
How full you fill each pot, as a share of its volume. 85-95% is typical, leaving room to water.
Bags & Cost
Coco and potting mix are often sold in 50 L bags.
Optional. Leave blank to skip the cost.
Extra media for spillage and settling, from 0 to 50%. Blank means none.
Weight (optional)
After the first calculation, results update as you change a value.
How it's worked out · Sources
Media and bags
- Media per pot = pot volume × fill level.
- Total media = media per pot × number of pots × (1 + buffer).
- Bags = total media ÷ bag size, rounded up to whole bags. A total that is an exact number of bags needs exactly that many.
- The bag size starts at 50 L. In US units it shows as 13.2 US gal but is counted as 50 L until you type your own size, which is used as typed.
- Cost = bags × price per bag; cost per pot = cost ÷ number of pots. Money, the price per bag included, is rounded to the nearest cent.
Pot shapes
- A round pot is measured as a straight cylinder from its top diameter. A pot that narrows to its base holds less: one 26 cm across the top, 20 cm at the base and 26 cm tall holds 10.9 L, about 21% less than the 13.8 L cylinder. So the estimate errs toward more media.
- A square or rectangular pot is length × width × height.
- Gallons here are US gallons (3.785 L). An imperial gallon is larger, 4.546 L.
Weight
The weight is for the media your pots need, buffer included. Media left over in whole bags isn't counted, so the bags you carry can weigh more. It is only as good as the density behind it: a bag's weight depends on the product, how moist it is and how loosely it is packed, and wet media weighs more. Each listed product's figure is the maker's own:
Hydro Oasis • Substrate Volume & Cost Calculator