Greenhouse Sizing Calculator
Calculate greenhouse footprint from plant count, growing style, and spacing.
Returns length, width, and square footage for hobby and commercial growers.
Greenhouse sizing depends on what you want to grow, how many plants you need, and your available space. Getting the right size prevents overcrowding and ensures adequate light and air circulation.
Space requirements by plant type:
| Plant Type | Space Per Plant | Plants Per Sq Ft |
|---|---|---|
| Seedling trays | 0.5 sq ft (0.05 sq m) | 2 |
| Herbs | 1 sq ft (0.09 sq m) | 1 |
| Lettuce and greens | 1 sq ft (0.09 sq m) | 1 |
| Tomatoes | 4 sq ft (0.37 sq m) | 0.25 |
| Peppers | 2 sq ft (0.19 sq m) | 0.5 |
| Cucumbers | 4 sq ft (0.37 sq m) | 0.25 |
| Potted flowers | 1.5 sq ft (0.14 sq m) | 0.67 |
Standard greenhouse sizes:
- Small (6x8 ft / 1.8x2.4 m): 48 sq ft. Good for hobby gardeners with 20-40 plants.
- Medium (8x12 ft / 2.4x3.7 m): 96 sq ft. Room for benches and a good variety.
- Large (10x16 ft / 3.0x4.9 m): 160 sq ft. Serious growing with walkways.
- Extra Large (12x20 ft / 3.7x6.1 m): 240 sq ft. Near-commercial capacity.
Important considerations:
- Subtract 30% of floor space for walkways and work areas.
- Benches and shelving can effectively double your growing space by using vertical layers.
- Minimum recommended width is 6 feet (1.8 m) to allow a center walkway.
- Orient the long side east-west for maximum winter sun exposure in the Northern Hemisphere.
- Ventilation: at least 20% of the floor area should be openable vents or windows.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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