Fill volume and soil blend proportions
A bed’s fill volume tells you how much space to fill. A blend calculation divides that space among ingredients. Shares are fractions of volume, not weight: 0.5 means half the fill volume. The arithmetic checks the recipe you enter; it does not select a recipe for every bed.
Measure and calculate
- Find the bed’s internal fill volume in cubic feet; a 4 by 8 ft bed filled 1 ft deep holds 32 ft³.
- Enter a volume share for each ingredient. The three shares must add up to 1, including zero for any unused ingredient.
- Choose a component to see its volume, then use that component’s package size when purchasing.
Component volume = total fill volume × component volume share.
A worked example
- Inputs
- A 32 ft³ bed uses a declared 50% topsoil, 50% compost blend with no soilless media.
- Calculation
Topsoil: 32 × 0.5 = 16 ft³. Compost: 32 × 0.5 = 16 ft³.- Result
- 16 ft³
The initial output is 16 ft³ of topsoil. Switch to compost for the other 16 ft³. This preset describes a particular starting-soil scenario; it is not a universal recommendation for raised beds or containers.
Read the result
| Output or check | What it means for your project |
|---|---|
| Component volume: ft³ | Each result is one ingredient, not the full bed. In the example, 16 ft³ topsoil plus 16 ft³ compost accounts for all 32 ft³. |
| Volume shares: 0–1 | Use 0.5 for 50%. All three shares must total 1; use 0 for an ingredient you are not including. |
| Ordering each ingredient | Convert each component volume using its own bag size or bulk unit. A calculated split does not establish whether a recipe suits the plants or drainage conditions. |
Common questions
Do I enter 50 or 0.5 for a 50% share?
Enter 0.5. Entering percentages as whole numbers would multiply the requested volume by the wrong scale.
Why do all shares have to add up to 1?
Together the ingredients must account for the whole stated fill volume. If the shares total 0.9, 10% of the recipe is missing. Check actual combined volumes when materials settle or mix non-additively.