Grow Light Calculator

Calculate the number of grow light fixtures needed and Daily Light Integral (DLI) from PPFD, photoperiod, and canopy area for optimal indoor plant growth.

Inputs

Fixture PPFD

µmol/m²/s

Light Hours per Day

hrs

Canopy Area

sq ft

Fixture Coverage

sq ft

Tab to move between fields

Results

Fixtures Needed

Daily Light Integral (DLI)

34.56 mol/m²/day

DLI RatingExcellent (fruiting crops)

Est. Watts per Fixture357 W

Total Power Draw713 W

Daily Energy Use11.42 kWh

Monthly Energy Use342 kWh

Est. Monthly Electric Cost$41.10

How to Use This Calculator

Enter the PPFD output and light hours per day for your fixture, along with your total canopy area in sq ft.
Review Fixtures Needed and Daily Light Integral (DLI) — most vegetables need 15–30 mol/m²/d for optimal growth.
Enter your electricity cost per kWh to get the Est. Monthly Electric Cost.
Use Total Power Draw (W) to verify your electrical circuit has sufficient capacity for your lighting setup.
Check DLI Rating to confirm your light level is appropriate — the calculator will flag if DLI is too low or too high for your crop.

How the result changes with Canopy Area

Canopy Area	Fixtures Needed	Daily Light Integral (DLI)
1,001	63	34.56 mol/m²/day
3,501	219	34.56 mol/m²/day
6,500	407	34.56 mol/m²/day
9,000	563	34.56 mol/m²/day

What each input means

Fixture PPFD: Photosynthetic Photon Flux Density at canopy height in micromoles per square meter per second. Check your fixture's spec sheet for PPFD at your hanging height.
Light Hours per Day: Photoperiod in hours per day. Vegetative growth: 16-18 hrs. Flowering: 12 hrs. Leafy greens: 14-18 hrs.
Canopy Area: Total plant canopy area to illuminate in square feet. Measure the growing surface, not floor space.
Fixture Coverage: Area each fixture effectively covers in square feet at your hanging height. A 4x4 ft fixture covers 16 sq ft.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Fixture PPFD = 600, Light Hours per Day = 16, Canopy Area = 32, Fixture Coverage = 16 = 4 input(s) provided
Calculate Fixtures Needed
Fixtures Needed
2 = 2
Calculate Daily Light Integral
Daily Light Integral
34.56 = 34.56
Calculate DLI Rating
DLI Rating
Excellent (fruiting crops) = Excellent (fruiting crops)
Calculate Est. Watts per Fixture
Est. Watts per Fixture
357 = 357