Greenhouse Size Calculator
Size a greenhouse from the number of plants you want to grow and the bench space needed.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Estimate bench space, a minimum rectangular footprint and rough interior volume from plant count, bench layout, path width and eave height. The volume assumes a gable roof rising 1.5 ft above the eaves. These are layout estimates; verify clearances, framing, ventilation and local conditions before building.
Worked example
calculated with the default values below
Number of plants to grow 40 · Bench space per plant 1.5 sq ft · Bench layout Both long sides · Path width 2 ft · Eave height 6 ft Bench space required 60.0 sq ft · Minimum greenhouse width 6.0 ft · Minimum greenhouse length 15.0 ft · Floor area 90.0 sq ft · Approx. interior volume (1.5 ft roof rise) 608 cu ft
Method and assumptions
B = n × s; w = max(6,w₀); l = max(8,l₀); A = w × l; V = A × (h + 0.75) Minimum dimensions are 6 ft wide and 8 ft long. Volume assumes a gable roof with a fixed 1.5-ft rise, so its average roof cross-section adds 0.75 ft above the eaves. Both long sides: (w₀,l₀) = (4+p,B/4); One side only: (w₀,l₀) = (2+p,B/2); Central island bench: (w₀,l₀) = (4+2p,B/4) Estimate bench space, a minimum rectangular footprint and rough interior volume from plant count, bench layout, path width and eave height. The volume assumes a gable roof rising 1.5 ft above the eaves. These are layout estimates; verify clearances, framing, ventilation and local conditions before building. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Data sources
The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Disclaimer
These are general gardening estimates. Planting windows, growth, water and nutrient needs vary by place and plant. Check local extension guidance and product labels before acting on an estimate.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
B = n × s; w = max(6,w₀); l = max(8,l₀); A = w × l; V = A × (h + 0.75)
- n
- plants
- s
- bench area per plant (sq ft)
- w,l
- estimated width and length (ft)
- A
- floor area (sq ft)
- h
- eave height (ft)
- V
- interior volume (cu ft)
Minimum dimensions are 6 ft wide and 8 ft long. Volume assumes a gable roof with a fixed 1.5-ft rise, so its average roof cross-section adds 0.75 ft above the eaves. Both long sides: (w₀,l₀) = (4+p,B/4); One side only: (w₀,l₀) = (2+p,B/2); Central island bench: (w₀,l₀) = (4+2p,B/4)
Frequently asked questions
Why does bench layout change the greenhouse size?
The layout sets the bench and path widths, and the plant count plus space per plant determines bench area and length. For 40 plants at 1.5 sq ft each, two 2-ft benches with a 2-ft path need about 6 × 15 ft. The volume estimate uses that 90 sq ft floor area times a 6-ft eave plus a 0.75-ft average roof section, assuming a 1.5-ft gable rise.
Which inputs and limits apply to Greenhouse Size Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Number of plants to grow: 1–2,000; Bench space per plant: 0.3–10 sq ft; Path width: 1–6 ft; Eave height: 4–12 ft B = n × s; w = max(6,w₀); l = max(8,l₀); A = w × l; V = A × (h + 0.75) Minimum dimensions are 6 ft wide and 8 ft long. Volume assumes a gable roof with a fixed 1.5-ft rise, so its average roof cross-section adds 0.75 ft above the eaves. Both long sides: (w₀,l₀) = (4+p,B/4); One side only: (w₀,l₀) = (2+p,B/2); Central island bench: (w₀,l₀) = (4+2p,B/4) Estimate bench space, a minimum rectangular footprint and rough interior volume from plant count, bench layout, path width and eave height. The volume assumes a gable roof rising 1.5 ft above the eaves. These are layout estimates; verify clearances, framing, ventilation and local conditions before building. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
What is a complete worked example for Number of plants to grow = 40; Bench space per plant = 1.5 sq ft?
Inputs: Number of plants to grow = 40; Bench space per plant = 1.5 sq ft; Bench layout = Both long sides; Path width = 2 ft; Eave height = 6 ft. Calculation: B = n × s; w = max(6,w₀); l = max(8,l₀); A = w × l; V = A × (h + 0.75). Results: Bench space required = 60.0 sq ft; Minimum greenhouse width = 6.0 ft; Minimum greenhouse length = 15.0 ft; Floor area = 90.0 sq ft; Approx. interior volume (1.5 ft roof rise) = 608 cu ft.