What you need to know:
- Lumens the manufacturer says your bulb emits. If you don't know this, you can use the wattage and calculate your watts/lumens using a table like this.
- Area in m^2 of what you want to cover with your lights.
- Distance of your light from your plants OR desired lux you want falling on your plants.
What the calculator will estimate:
- If you enter the current distance of your lights from your plants, it will give you the estimated lux on your plants.
- If you enter the desired lux for your plants, it will suggest the appropriate distance to achieve this amount.
You can download the spreadsheet here: