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Daily Light Integral (DLI) Calculator.

Calculate DLI from measured PPFD and photoperiod hours.

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Daily light integral: 23.04 mol/m²/day

Daily light integral

23.0400mol/m²/day

Educational arithmetic only. Enter measured values and keep units consistent. No crop, feed, veterinary, or experimental recommendation is inferred.

Use Cases

Optimize Indoor Grow Lighting

Determine if your current PPFD and photoperiod provide sufficient daily light for your plants. Adjust light intensity or duration to hit target DLI for healthier growth.

Example: For lettuce needing 17 mol/m²/day, set PPFD to 400 µmol/m²/s and photoperiod to 12 hours to get DLI 17.3.

Greenhouse Supplemental Lighting

Calculate the DLI contribution from supplemental lights to ensure consistent growth during cloudy days or winter months.

Example: If your greenhouse gets 10 mol/m²/day from sunlight, add 10 more with lights to reach 20 for tomatoes.

Frequently Asked Questions

What is DLI and why is it important for plants?
DLI (Daily Light Integral) is the total amount of photosynthetically active radiation (PAR) plants receive in a day, measured in mol/m²/day. It's crucial because it directly influences photosynthesis, growth, and yield. Different plants have different DLI requirements, so knowing your DLI helps you adjust lighting to meet their needs.
How is DLI calculated from PPFD and photoperiod?
DLI is calculated by multiplying the average PPFD (in µmol/m²/s) by the photoperiod (in hours) and then converting to mol/m²/day. The formula is: DLI = PPFD × photoperiod × 3600 / 1,000,000. For example, 500 µmol/m²/s for 12 hours gives a DLI of 21.6 mol/m²/day.
What are typical DLI requirements for common plants?
Low-light plants like ferns and some houseplants need 5-10 mol/m²/day. Medium-light plants like herbs and leafy greens thrive with 15-25. High-light plants like tomatoes, peppers, and cannabis require 25-50 or more. Use this calculator to see if your current lighting meets your plants' needs.

Tips & Common Mistakes

Tips

  • Measure PPFD at the canopy level, not at the light source, to get accurate readings for your plants.
  • Consider the photoperiod for your specific plant stage; many plants need longer days during vegetative growth and shorter during flowering.
  • Use a quantum sensor to measure PPFD, as regular lux meters do not measure PAR accurately.
  • Remember that DLI is cumulative; even low PPFD over a long photoperiod can meet plant needs.

Common Mistakes to Avoid

  • Using PPFD measured at the light source instead of at the plant canopy, leading to overestimated DLI.
  • Forgetting to convert units correctly; ensure PPFD is in µmol/m²/s and photoperiod in hours to get DLI in mol/m²/day.
  • Assuming all plants have the same DLI requirement; always check specific needs for your plant species.

Last updated: August 13, 2026