Grow Light Bulb Wattage Calculator

Determining the wattage of your grow light is important for a successful indoor garden.

Recommended wattage is 50 watts of grow light per square foot in the growing area.

When entering your data, round up to the next foot or use decimals for more accuracy.

(Enter the length of your growing area in feet)

(Enter the width of your growing area in feet)

(Total square feet of your growing area needed)

(Approximate watts needed for your indoor garden area)

WATTS (Estimate Only)

Many of us live in areas where gardening outdoors in the fall/winter months is simply not possible. But, if you love to garden, there's no reason why you shouldn't keep it up through the winter months.

In considering the correct wattage for your area, keep in mind that although higher wattage will equate to bigger yields, it will also mean higher energy consumption and more heat output to consider.

LED lighting is the newest form of horticultural lighting on the market.

The growth you'll experience under LED lighting may be kind of slow. The advantages to using LED's is that there is very little electrical usage, and almost no heat to deal with. If you've got a very small space that can't be ducted to remove heat, LED's may be the best answer for you.

The next generation in fluorescent lighting includes the new T-5 lights.

These new lights have extremely high output but are energy efficient and long lasting.

The T-5 lights triple the light output of normal fluorescent lights without increasing the wattage. Plants absorb a high percentage of T-5 lighting because the fixtures function well very close to plants. High output bulbs require a high output fixture to operate, so the bulbs and normal fluorescent fixtures will not work together.

Plant with Recommended Footcandles


Grow Your Own Indoor Vegtables.

Pepper (Sweet)
Sweet Pea




A foot-candle is a measurement of light intensity.

One foot-candle is equal to 10.76 Lumens. This means that you need to take your foot-candles measurement and multiply it by 10.76. Using an example of 50 foot-candles, we get the following equation: 50 x 10.76. By working out this calculation, you will be able to get 538 lumens.

1000 foot candles x 10.76 lumens = 1000 x 10.76 = 10760 lumens.

Converting into Watts

The next thing that you can do is to calculate the number of watts. This is very easy to do once you have converted into watts. One lumen is equal to 0.001496 watts. This means that you simply need to take your answer and multiply it by 0.001496. In our example, 10760 x 0.001496 equals 16.09 watts per square meter. Write this down again, and you can use it to work out anything you want to know.

1 square meter = 10.7639 square feet.   1 square foot = .092903 square meter.  100 square feet = 9.2903 square meters

So a 100 square foot area would require 16.09 x  9.2903 = 149.480 Watts at 1000 Foot Candles Intensity

Use This Calculator For Calculations

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