Grow Light Calculator

Calculate grow light wattage, daily light integral (DLI), hanging height, photoperiod hours, and electricity cost for indoor growing.

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How It Works

Grow lights replace sunlight for indoor plants. The key metric is DLI (Daily Light Integral) -- the total amount of photosynthetically active light a plant receives in a day, measured in mol/m2/day. Leafy greens need 10-14 DLI, fruiting plants need 20-30 DLI, and seedlings need 8-12 DLI. LED lights are the most efficient option today, producing the most light per watt of electricity with the least heat. Fluorescent lights (T5) are good for seedlings and herbs. HPS (high-pressure sodium) lights are powerful but hot and energy-hungry. Hanging height matters: too close burns leaves, too far wastes light. Adjust height as plants grow. A timer is essential -- inconsistent photoperiods stress plants and reduce yield.