DLI Calculator

What it does

DLI ("daily light integral") is the total amount of photosynthetic light a square metre of canopy receives in a day, in moles. PPFD is the instantaneous intensity; multiplying it by the hours the lights are on turns it into a daily dose, which is what crop light targets are written in.

When to use it

When you have a PPFD reading or fixture plan and a photoperiod and want the daily dose — or when you have a crop DLI target and need to know either the PPFD to run at your photoperiod or how many hours to run at your PPFD.

How it calculates

• DLI = PPFD × photoperiod × 3,600 s/h ÷ 1,000,000 µmol/mol. At 400 µmol/m²/s for 16 h that is 23.04 mol/m²/day.
• Gap to Target = target − delivered DLI. A negative gap means this PPFD and photoperiod already exceed the target.
• This is the supplemental (electric) light only. In a greenhouse, add the natural DLI — use Solar DLI or Crop DLI Analysis for that.

What you enter

PPFD (µmol/m²/s)

Photosynthetic photon flux density at the canopy — a quantum-sensor reading or your fixture plan's average.

Photoperiod (hours/day)

Hours per day the canopy receives that PPFD.

Target DLI (mol/m²/day)

Optional. The daily light integral you are steering to; drives the "needed" outputs below.

What you get

DLI (mol/m²/day)

PPFD Needed for Target at this Photoperiod (µmol/m²/s)

Hours Needed for Target at this PPFD (h/day)

Gap to Target (mol/m²/day)

Reading the result

DLI is what the canopy gets per day. If the Gap to Target is positive, either raise PPFD to the "PPFD Needed" value or lengthen the photoperiod toward "Hours Needed"; if the hours needed exceed a sensible photoperiod for the crop, you need brighter fixtures or more of them, not longer days.

Related calculators

• Crop DLI Analysis
• Solar DLI Calculator
• PPFD Uniformity Estimator
• Light Recipes