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Grow Room Calculator

Plan indoor grow room dimensions, plant capacity, lighting, and ventilation CFM requirements for hydroponic cultivation.

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Inputs that matter
Room Length, Room Width, Room Height, Plant Count, and 1 more
Output to expect
Grow Room Planner
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Plant Capacity

Lettuce: 4–6 plants/sq ft. Cannabis: 1 plant/4–9 sq ft. Tomatoes: 1 plant/4 sq ft. Spacing depends on crop and training method.

Plants = Floor area ÷ Spacing² per crop

Lighting Power

Modern LEDs achieve target PPFD at 30–50 W/sq ft. Older HID needed 50–65 W/sq ft. Match to DLI targets for your crop.

Watts ≈ 30–50 W/sq ft (modern LED) for high-light crops

Ventilation CFM

Target 20–60 air exchanges per hour depending on heat load. Add 25% for duct friction and filter resistance.

CFM = Room volume (cu ft) × Air exchanges/hr ÷ 60

Updated: July 2026

Example Scenarios

64 sq ft supports 9–16 cannabis plants at 4–7 sq ft each. Two 480W LED fixtures, 800 CFM exhaust for heat and odor control.

6 sq ft fits 1–2 small plants. 100W LED, 50 CFM inline fan with carbon filter for odor management.

1000 sq ft floor with 4-tier racks = 4000 sq ft growing area at 5 plants/sq ft — 20,000 heads per cycle.

FAQ

Depends on crop and training. Cannabis: 1 per 4 sq ft (SCROG) to 1 per 9 sq ft. Lettuce: 4 plants per sq ft. Calculate from mature canopy size, not seedling spacing.

Calculate room volume × desired air exchanges per hour. LED grows: 20–30 ACH. HID grows: 40–60 ACH. Add CFM for temperature control above ambient.

Minimum 7 ft for most crops. Cannabis with training: 8–10 ft. Vertical farming racks need 8–12 ft depending on tier count and fixture height.

Insulation stabilizes temperature, reduces energy costs, and prevents condensation. Reflective Mylar or white paint improves light distribution.

Plants transpire heavily during lights-on. Estimate 0.5–1 gallon water transpired per day per mature plant. Size dehumidifier for peak load plus ambient humidity.

About Grow Room Calculator

Design an efficient grow room by calculating usable plant capacity, lighting requirements, ventilation CFM, and environmental load from your room dimensions and cultivation goals.