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Randozi
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DLI and PPFD Calculator

Turn the light your plants receive into a daily light integral — or work backwards to the PPFD or hours that reach the DLI you are aiming for.

Daily light integral

14.4 mol/m²/day

250 µmol/m²/s for 16 h

How it works

  1. Pick what you want to find: the DLI, the PPFD needed, or the hours needed.
  2. Enter the values you know: PPFD in µmol/m²/s, light hours per day, or a target DLI in mol/m²/day.
  3. Read the result and the matching values for the other two quantities.
  4. Adjust the hours or the light height and measure PPFD again with a quantum meter.

What people use it for

  • Seedlings and herbs

    Check that an LED panel on a 16-hour timer delivers the daily light a crop needs.

  • Choosing a photoperiod

    See how many hours a fixed-output light must stay on to reach a target DLI.

  • Comparing lights

    Turn a PPFD reading at canopy height into a daily number you can compare across fixtures.

Questions

What is the formula?
DLI (mol/m²/day) = PPFD (µmol/m²/s) × light hours × 3,600 ÷ 1,000,000. For example 250 µmol/m²/s for 16 hours gives 14.4 mol/m²/day.
Does this work for sunlight?
Not directly. The formula assumes a constant PPFD all day, which is true for a fixed grow light but not for the sun or a dimmed schedule. For those, log PPFD over time and add it up.
What DLI does my plant need?
It varies by species and growth stage, so check the grower's guide for your crop. This tool only converts between PPFD, hours and DLI; it does not recommend a target.