Biology
Turn grow-light PPFD and hours into the daily light integral plants receive.
Your inputs
Change any value — everything updates instantly.
From a light meter or the lamp's spec sheet.
How long the lights are on.
Try an example
Daily light integral
23 mol/m²/day
This means each square metre of leaves gets 23 moles of usable light per day.
What you are seeing
The sun-shaped lamp shines on a plant; the bar below fills through the day.
Light is on for 16 of 24 hours.
By the end of the day the plant has collected 23 mol/m².
Light per hour
1.44 mol/m²/h
Light collected each hour.
Plant group
Very high light
Rough fit for plant types.
Result explanation: Is it enough light?
DLI = 23 mol/m²/day.
Real-life comparison: Lettuce ~12–17, tomatoes ~20–30, many houseplants ~3–10.
Low, normal or high? Good for fruiting crops.
DLI against photoperiod
How to read this chart: More hours means more total light. The red dot is your setting.
Adds up the usable light a plant receives across the day.
23 mol/m²/day.
Raise hours or intensity to increase DLI.
Too much light can stress shade plants.
Seconds of light × intensity, converted to moles.
DLI = PPFD × hours × 3,600 ÷ 1,000,000
Symbols
Why this formula works
PPFD is light per second; multiplying by total seconds gives the day's total.
Unit check
µmol/m²/s × s = µmol/m² → ÷10⁶ = mol/m² ✓
Worked example
Common mistakes
DLI is 23 mol/m²/day.
The amount of plant-usable light hitting a surface each second.
Only with a conversion factor that depends on the light source; PPFD is better.
Many plants need a dark period; follow crop guidance.
Yes — it drops as the light moves further away.
Reviewed 2026-09-25 · Next review 2027-09-25
Important limitation. Educational estimate; measure at canopy height.
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