Seed Tray Size and Capacity Guide
Tray labels mix two different things: the physical footprint and the number of growing cells. Keep those separate so a 32-cell tray and a 72-cell tray do not look like different shelf sizes by mistake.
Try your own numbers
4 container groups · 4 standard tray spaces
Check the whole seasonA footprint is not a cell count
Several inserts can occupy the same carrying-tray footprint. A full tray with fewer larger cells still uses a full tray space. A half tray uses half a standard footprint only if its actual outside dimensions and arrangement support that fit.
Create profiles for your equipment
The included 72-, 50-, and 32-cell profiles are editable capacity examples. Pot-group profiles use stated counts such as 12 pots per tray; check your real pots, rims, spacing, and carrying trays. Dimensions in the profile are references; the reserved footprint drives calculations.
Understand rounding
Seedling Space rounds up to complete tray or pot-group units. A batch with 73 plants needs two 72-cell trays unless you explicitly use another arrangement. When you choose shared starting trays, compatible batches fill spare cells and overflow into another matching tray. Separate batches still reserve their own whole containers. Check growing conditions before sharing; the planner does not prove biological compatibility.
Worked example
36 cells in a half-tray profile with footprint 0.5 means 48 seedlings need two units: 2 × 0.5 = 1 standard tray space.
These calculations describe space and time, not guaranteed plant performance. Use your actual equipment and crop-specific growing guidance.
Related tools
- A Seed Starting Spreadsheet Alternative
- How Many Seed Trays Do I Need?
- How Many Seedlings Fit Under a 4-Foot Grow Light?