Cannabis Light Plan Calculator

Fixture count and wattage from canopy area and target PPFD.

Inputs

Canopy area (sq ft)

Target PPFD (µmol/m²/s)

Fixture type (0-3)

Photoperiod (hrs/day)

Hang height (inches)

Tab to move between fields

Results

Fixtures needed

Total wattage4,200

Achieved PPFD1,009

Daily Light Integral (DLI)65.4

Heat output (BTU/hr)14,330

Amps (120V)35

Amps (240V)17.5

Monthly kWh2,268

Monthly electricity ($)$272.16

How to Use This Calculator

Enter total canopy area in sq ft and your target PPFD (µmol/m²/s) for the growth stage.
Select fixture type (HPS, CMH, LED mid-tier, LED top-tier) and photoperiod (hours/day).
Set hang height in inches above the canopy.
Review Fixtures Needed, Total Wattage, Achieved PPFD, DLI, and Monthly Electricity Cost.
Aim for a DLI of 40–65 mol/m²/day during flowering for maximum yield.

How the result changes with Canopy area (sq ft)

Canopy area (sq ft)	Fixtures needed
5,001	313
17,501	1,094
32,500	2,032
45,000	2,813

What each input means

Canopy area (sq ft): Total plant canopy area in square feet.
Target PPFD (µmol/m²/s): Target photosynthetic photon flux density. Veg: 400-600, Flower: 600-1000+.
Fixture type (0-3): 0 = HPS 1000W, 1 = CMH 315W, 2 = LED mid-tier, 3 = LED top-tier.
Photoperiod (hrs/day): Hours of light per day (veg typically 18, flower 12).
Hang height (inches): Distance from light to canopy in inches.

What each result means

Fixtures needed: Number of light fixtures required.
Total wattage: Combined wattage of all fixtures.
Achieved PPFD: Estimated PPFD delivered at canopy level.
Daily Light Integral (DLI): Total light energy per day (mol/m²/day). Cannabis flower target: 40-65.
Heat output (BTU/hr): Total heat generated by lights for HVAC sizing.
Amps (120V): Total amperage on 120V circuits.
Amps (240V): Total amperage on 240V circuits.
Monthly kWh: Monthly electricity consumption.
Monthly electricity ($): Estimated monthly electricity cost at $0.12/kWh.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Canopy area (sq ft) = 100, Target PPFD (µmol/m²/s) = 800, Fixture type (0-3) = 2, Photoperiod (hrs/day) = 18 = 5 input(s) provided
Calculate Fixtures needed
Fixtures needed
7 = 7
Calculate Total wattage
Total wattage
4200 = 4200
Calculate Achieved PPFD
Achieved PPFD
1009 = 1009

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