The Ultimate Grow Light Calculator
Welcome to the most advanced grow light calculator available to hydroponic growers.
Stop guessing your light height, intensity, or how many lights you need. This free, professional-grade tool eliminates the guesswork by giving you scientifically-backed data for your specific setup. Whether you're growing delicate herbs or high-yield tomatoes, our calculator will help you dial in the perfect lighting for explosive growth and maximum yields.
This tool helps you calculate:
- Required Average PPFD: The exact light intensity your plants need.
- Target DLI: The total amount of light your plants should receive daily.
- Recommended # of Lights: How many lights you need for your space.
How to Use the Calculator
Standard Mode (For Planning Your Setup)
This is the perfect mode for designing a new grow space or upgrading your current one.
- Enter Your Area Dimensions: Input the length and width of your grow space.
- Select Your Plant Type: Choose between Low, Medium, or High-Light plants. (See definitions below if you're unsure).
- Choose the Growth Stage: Select whether your plants are seedlings or in the vegetative or flowering stage.
- Enter Your Light's Wattage: Input the wattage of a single light fixture you plan to use.
- Adjust the Light Schedule: Use the slider to set how many hours your lights will be on per day.
- Get Your Results: The calculator will instantly show you the number of lights you need and the target PPFD you should aim for.
Inverse Mode (For Optimizing an Existing Setup)
Already have your lights and a PAR meter? This mode is for you. It lets you find out the exact DLI you're currently providing.
- Toggle to Inverse Mode: Click the switch at the top of the calculator.
- Enter Your Measured PPFD: Input the average PPFD reading you get from your PAR meter.
- Set Your Light Schedule: Use the slider to set your current light-on hours.
- See Your DLI: The calculator will instantly show you your actual Daily Light Integral. You can then adjust your light height or dimmer settings to match your plant's target DLI.
Why This Calculator is Different
Most online calculators only tell you a generic wattage recommendation. This is outdated and inaccurate. Modern LED grow lights are incredibly efficient, and the real metrics for plant growth are PPFD (light intensity) and DLI (total daily light).
Our calculator is built on current horticultural research to provide recommendations based on what truly matters. By accounting for your specific plant type, its growth stage, and your light schedule, we can give you a far more precise and effective lighting plan, saving you money on electricity and preventing you from buying more lights than you need.
Grow Light Calculator
Determine the ideal light intensity (PPFD) and number of lights needed for your grow space.
1. Your Grow Setup
2. Your Lighting Results
Understanding Plant Light Needs
Low-Light Plants
Optimal DLI: 8-18
These plants, including microgreens and most leafy greens, thrive without intense light and do not bear heavy fruits.
Examples: Lettuce, Spinach, Kale, Mint, most Herbs.
Medium-Light Plants
Optimal DLI: 15-25
This category includes high-performing leafy greens and plants that produce smaller fruits or flowers.
Examples: Strawberries, Basil, smaller Pepper varieties, most flowering ornamentals.
High-Light Plants
Optimal DLI: 25-45+
Sun-loving plants that require significant energy to produce large, dense fruits and flowers. This is the target for most fruiting vegetables.
Examples: Tomatoes, Cannabis, Cucumbers, large Peppers.