DLI Calculator: Calculate Accurate Daily Light Integral

Enter the following values (current input values are default for example purpose):

*NOTE: The DLI output recommendation for a specific plant is to be taken as a general guideline. The exact amount may vary based on factors such as PPFD, no. of hours the lights are on in a day, etc.

What is Daily Light Integral (DLI)?

Daily Light Integral, or DLI, measures the amount of photosynthetically active light a plant receives in one 24-hour period.

It is expressed as moles of light photons per square meter per day, or mol/m2/d.

Getting adequate DLI is absolutely vital for plants to grow strongly and stay healthy.

Light fuels photosynthesis and other processes that feed plant growth, development, yield, and visual appeal.

However, precisely quantifying and supplying the optimal DLI levels can pose substantial difficulties for home gardeners and professional plant producers alike.

Lux, lumen, PAR, PPFD—making sense of all the different DLI metrics and calculations can be bewildering.

And without proper DLI, plants suffer—from weakened, stunted growth under low light to burned, damaged leaves if DLI exceeds tolerances.

That’s why we created an accessible, easy-to-use DLI calculator tailored to popular garden plants.

Take the complication and guesswork out of daily light requirements with science-backed guidelines and recommendations.

Daily Light Integral Metrics Explained

Wondering what all those scientific-sounding terms used to measure light actually mean? Let me break down the key plant lighting metrics into simple, everyday language.

Understanding measurements like PAR, PPFD, and lux is crucial for calculating the optimal Daily Light Integral (DLI) for your indoor and outdoor vegetation.

Photosynthetically Active Radiation (PAR)

PAR represents the spectral range of sunlight that plants use for photosynthesis. It’s expressed as micromoles per square meter per second, or μmol/m2/s.

Basically, PAR tells you how much usable light is available to power plants’ food-making processes at any given moment.

For context, outdoor PAR levels on a sunny summer day generally measure around 2,000 μmol/m2/s.

Optimizing indoor PAR between 200 and 1,000 μmol/m2/s encourages strong photosynthetic activity.

Getting PAR in the right zone ensures plants have enough energy to thrive!

Photon Flux Density (PPFD)

Closely related to PAR, the PPFD metric indicates how many photon particles hit a given surface over time. So it conveys the density of usable light striking plants’ leaves and stems.

PPFD is measured as micromoles per meters squared per second – μmol/m2/s.

Target PPFD levels vary based on factors like plant variety and growth stage, but often range from 300 to 1,000 μmol/m2/s for optimal development.

To be very specific:

  • Seedlings: 100-300 μmol/m2/s
  • Vegetative growth: 300-600 μmol/m2/s
  • Flowering/fruiting: 600-1000+ μmol/m2/s

So monitoring PPFD helps ensure your crops or houseplants get just the right light intensity for flourishing photosynthesis without risk of light stress.

Foot-candles and Lux Measurements

Foot candles and lux gauge brightness from a human visual perspective. Foot candles are commonly used in the US, while lux measurements are favored internationally.

However, since plants experience light differently than people, these units only indirectly relate to DLI and photosynthetic activity.

Converting lux and foot-candles to μmol/m2/s allows calculating a DLI target tailored to your plant’s specific needs.

For example, orchids thrive around 4-8 mol/m2/d DLI. To hit this with artificial lights, translate the lux rating to PAR or PPFD first, then derive the corresponding DLI.

Make sense?

Now that you understand the essential measurements, let’s use them to calculate the ideal daily light integral!

How To Calculate DLI

Figuring out whether your veggies, herbs, or houseplants are getting the optimal daily light is crucial for growth.

That’s where the Daily Light Integral comes in. Here’s how you can easily calculate DLI and dial in just the right light levels.

The DLI calculation requires just two variables:

  1. Hours of daily light: Generally how many hours per day your lamps or natural sunlight illuminate the plants.
  2. Light intensity: Measured as PPFD (Photosynthetic Photon Flux Density), or the number of micromoles of photons hitting a square meter every second.

Once you know the hours and intensity (PPFD), the DLI formula is:

DLI = Hours of light x PPFD x 0.0036

That 0.0036 is simply a conversion factor.

When you multiply it with the light duration and intensity, it converts things to the proper DLI scale of mol/m2/day that plants require.

Dhruvir Zala

Meet your guide
Dhruvir Zala

I’m the guy behind Farmingram, where I nerd out on all things indoor agriculture. Through rigorous research, my goal is to get more people excited about where agriculture is headed.