Rockwool Cube Calculator

Number of plants or starts

Total seedlings, clones, or starts you plan to root.

Cubes per plant

Use 1 for standard starts; increase for backups.

Waste / extra (%)

Adds extra cubes for losses and selection.

Cube length (cm)

Typical cubes are 2.5–10 cm.

Cube width (cm)

Match net cup or insert size.

Cube height (cm)

Height impacts root room and water holding.

Rockwool density (kg/m³)

Used only for dry mass estimation.

Pre-soak water (mL per cube)

Enter your usual conditioning volume per cube.

Pack size (cubes per pack)

Used for pack count and cost estimation.

Pack price

Leave 0 if you only need quantities.

Currency

Cost fields are numeric and currency-agnostic.

After calculating, results appear above this form.

Example Data Table

Sample scenario for a small propagation run:

Input	Value	Notes
Plants	24	Tray of starts
Cube size	4 × 4 × 4 cm	Standard small cube
Waste / extra	10%	Extra for weak starts
Pre-soak	120 mL per cube	Conditioning solution
Pack size	98 cubes	Typical retail pack

Formula Used

Base cubes = Plants × Cubes per plant
Required cubes = ceil(Base cubes × (1 + Waste% ÷ 100))
Cube volume (L) = (L × W × H in cm³) ÷ 1000
Total volume (L) = Required cubes × Cube volume
Estimated dry mass (kg) = Total volume (m³) × Density (kg/m³)
Pre-soak water (L) = Required cubes × Pre-soak mL ÷ 1000
Packs needed = ceil(Required cubes ÷ Pack size)
Total cost = Packs needed × Pack price

Tip: Conditioning usually means wetting cubes and stabilizing pH before planting. Follow your product guidance and nutrient program.

How to Use This Calculator

Enter how many seedlings or clones you plan to start.
Set cubes per plant and add a waste percentage for backups.
Type the cube dimensions in centimeters to match your product.
Enter your typical pre-soak volume per cube for planning water.
Optional: add pack size and price to estimate packs and cost.
Press Calculate to view results above the form.
Use Download CSV or Download PDF to save records.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.