Net Pot Count Calculator

Calculator inputs

Enter bed or tray dimensions, choose your layout, and calculate how many net pots fit with realistic allowances.

Units Millimeters (mm)Centimeters (cm)Meters (m)Inches (in)Feet (ft)

All dimensions use the same unit.

Bed length

Longest direction of the usable surface.

Bed width

Short direction of the usable surface.

Net pot diameter

Outside diameter of the pot rim.

Clear spacing between pots

Gap between pots for airflow and access.

Edge margin

Unusable border near tray walls or framing.

Layout pattern Grid (rows/columns) Staggered (offset rows)

Staggered can increase density in many beds.

Wastage allowance (%)

Covers spares, breakage, and setup changes.

Reserve pots (extra)

Adds a fixed number on top of wastage.

Plants per pot

Planning multiplier for seedlings or cuttings.

Use custom row and column counts

Custom rows

Custom columns

Use this when you already know your drilling jig layout.

Calculate Reset

Example data table

Typical raft or tray scenarios for quick reference.

Formula used

This calculator uses center-to-center pitch based on diameter and spacing.

• Usable Length = Length − 2 × Margin
• Usable Width = Width − 2 × Margin
• Pitch = Diameter + Spacing
• Grid: Columns = floor((Usable Length + Spacing) / Pitch), Rows = floor((Usable Width + Spacing) / Pitch), Count = Rows × Columns
• Staggered: vertical pitch is Pitch × √3/2, and odd rows are offset by half pitch.
• Recommended purchase: Recommended = Base + ceil(Base × Wastage%) + Reserve

How to use this calculator

1. Select units, then enter bed length and width.
2. Enter net pot diameter and your desired clear spacing.
3. Set edge margin to keep pots away from walls.
4. Choose grid or staggered layout for your plan.
5. Add wastage percent and any reserve pots.
6. Press Calculate to show results above the form.
7. Download CSV or PDF for project records.

Practical guidance for net pot planning

1) Why accurate net pot counts matter

Net pot quantity affects drilling templates, nutrient channel loading, lighting coverage, and stocking costs. A small mismatch can force re-drilling or leave dead zones where plants shade each other. This calculator converts your bed or tray dimensions into a repeatable count you can purchase and install.

2) Typical sizes and what they imply

Common net pot diameters include 2 in (about 5.1 cm) for leafy greens and 3 in (about 7.6 cm) for larger roots. Using a 2 in pot with 1 in clear spacing yields a pitch near 3 in, supporting tighter plant density. Larger pots often require wider spacing to maintain airflow and reduce humidity-related issues.

3) Spacing, margins, and real-world usability

Edge margin protects pots from tray walls, lids, and frame members; even 1–3 cm can prevent rubbing and leaks. Spacing is measured as clear gap between pots, then combined with diameter to form center-to-center pitch. If you plan to access plants for pruning or harvesting, increase spacing to improve reach and reduce leaf damage.

4) Grid versus staggered layouts

Grid patterns are easy to measure and drill because every row aligns. Staggered layouts offset alternate rows and can raise packing efficiency, often by roughly 5–15% depending on dimensions. The calculator estimates staggered rows using a vertical pitch of approximately 0.866 times the horizontal pitch.

5) Purchasing strategy with wastage and reserves

Add wastage to cover damaged pots, trial layouts, and future replacements; 3–8% is a practical range for many gardens. Reserve pots are useful when you expand rafts or add a propagation batch. The recommended purchase equals the base fit count plus wastage and your reserve value.

FAQs

1) Should I use grid or staggered?

Use grid for simple drilling and alignment. Use staggered when you want higher density and can keep offsets consistent across rows with a template or marked jig.

2) What spacing is recommended for leafy greens?

Many growers start with 2 in pots and 1–2 in clear spacing. Adjust upward if humidity is high or access is tight, and downward for early-stage seedlings.

3) Why does edge margin reduce my count so much?

Margins remove a full border around the tray. A 2 cm margin on each side reduces usable width by 4 cm, which can eliminate an entire row when pitch is small.

4) How do I choose wastage percent?

Use 3–5% for stable setups and careful handling. Use 6–10% if you expect frequent swaps, experimentation, or brittle materials that can crack during installation.

5) Can I plan multiple plants per pot?

Yes. Set “plants per pot” to your intended count. The calculator multiplies the recommended pots by that value to estimate total plants for sowing or transplant planning.

6) Why are my drilled holes not matching the estimate?

Hole centers may drift due to measuring, tool flex, or tray curvature. Verify your true center-to-center spacing and margins, then re-run the calculator or use custom rows and columns.

7) Does this work for round lids or irregular shapes?

This version assumes a rectangular usable area. For round or irregular lids, estimate an equivalent rectangle within the boundary, or use custom row and column counts based on your template.