Found this. Don't know how good this is but it's a start
2. WHAT IS THE SIZE OF YOUR GROW SPACE?
The size of your grow space will dictate the size and number of an LED units you purchase. A good rule-of-thumb for grow lights is to purchase
25-40 watts of actual power per square foot of growing space. For example, if you measured your growing space to be 16 square feet, you would want to purchase a
400 watt to
600 watt panel (assuming the plants are congregated in a single area). Furthermore, concentrating
100-160 watts of power per plant (or 4 square feet) will give your plants the energy they need to grow and flower.
If using many LED grow light panels for a larger grow, ensure that there is overlap in the light footprints. Doing so will allow all of your plants to receive the required light needed for superior growth. Therefore, more panels or larger panels are always a safe investment.
Below is a quick reference chart designed to help you determine the desired wattage based on your grow space. If you have a larger grow space, you can scale up from these numbers. Remember:
1 sq ft of grow space requires 25-40 watts of LED power.
Grow SpaceWattage
2 sq ft (2x1)
50-80
4 sq ft (2x2)
100-160
6 sq ft (2x3)
150-240
9 sq ft (3x3)
225-360
12 sq ft (3x4)
300-480
16 sq ft (4x4)
400-640
20 sq ft (4x5)
500-800
25 sq ft (5x5)
625-1000
30 sq ft (5x6)
750-1200
36 sq ft (6x6)
900-1440
40 sq ft (6x7)
1000-1600