Daily Light Integral (DLI) Calculator

Plant Lighting & Greenhouse Optimization Tool

Calculate the Daily Light Integral (DLI) for your plants using PPFD and light duration. Optimize your greenhouse or indoor grow setup for maximum yield and healthy growth.

Example Calculations

Try these sample lighting scenarios to see how the calculator works

Lettuce in Greenhouse (Single Light Period)

Greenhouse Lettuce

Lettuce grown under 16 hours of light at 300 μmol/m²/s.

PPFD: 300 μmol/m²/s

Light Hours: 16 hours/day

Unit System: Metric (mol/m²/day)

PPFD (Period 2): -

Light Hours (Period 2): -

Additional Period: No

Tomatoes Indoors (Supplemental Lighting)

Indoor Tomatoes

Tomatoes receive 10 hours of sunlight at 250 μmol/m²/s and 6 hours of supplemental LED at 600 μmol/m²/s.

PPFD: 250 μmol/m²/s

Light Hours: 10 hours/day

Unit System: Metric (mol/m²/day)

PPFD (Period 2): 600

Light Hours (Period 2): 6

Additional Period: Yes

Cannabis (High DLI)

Cannabis High DLI

Cannabis grown under 18 hours of light at 800 μmol/m²/s.

PPFD: 800 μmol/m²/s

Light Hours: 18 hours/day

Unit System: Metric (mol/m²/day)

PPFD (Period 2): -

Light Hours (Period 2): -

Additional Period: No

Ornamental Flowers (Two Light Periods)

Ornamental Flowers

Flowers receive 8 hours of sunlight at 200 μmol/m²/s and 8 hours of supplemental light at 400 μmol/m²/s.

PPFD: 200 μmol/m²/s

Light Hours: 8 hours/day

Unit System: Metric (mol/m²/day)

PPFD (Period 2): 400

Light Hours (Period 2): 8

Additional Period: Yes

Other Titles
Understanding Daily Light Integral (DLI): A Comprehensive Guide
Master plant lighting and optimize growth with accurate DLI calculations

What is Daily Light Integral (DLI)?

  • Definition and Importance
  • How DLI is Measured
  • DLI in Plant Growth
Daily Light Integral (DLI) is the total amount of photosynthetically active radiation (PAR) received by a given area over a 24-hour period. It is a key metric for understanding and optimizing plant growth in greenhouses and indoor farms.
Why DLI Matters for Plants
DLI directly influences plant health, yield, and development. Different crops have specific DLI requirements for optimal growth. Monitoring and adjusting DLI helps growers maximize productivity and quality.
How DLI is Calculated
DLI is calculated by multiplying the average PPFD (μmol/m²/s) by the number of light hours per day, then converting to mol/m²/day. The formula is: DLI = PPFD × hours × 0.0036.

DLI Calculation Examples

  • A greenhouse with 400 μmol/m²/s PPFD for 12 hours: DLI = 400 × 12 × 0.0036 = 17.28 mol/m²/day
  • Indoor grow with 600 μmol/m²/s for 18 hours: DLI = 600 × 18 × 0.0036 = 38.88 mol/m²/day

Step-by-Step Guide to Using the DLI Calculator

  • Input Your Lighting Data
  • Choose Units and Periods
  • Interpret Results
Our DLI calculator makes it easy to determine your daily light integral. Enter your PPFD and light hours, select your unit system, and optionally add a second light period for supplemental lighting.
Entering PPFD and Light Hours
PPFD is measured in μmol/m²/s and represents the intensity of light available for photosynthesis. Light hours indicate how long your plants receive this light each day. Both values are required for accurate DLI calculation.
Adding Multiple Light Periods
If your plants receive light from different sources (e.g., sunlight + LEDs), you can add a second period with its own PPFD and duration. The calculator will sum both periods for total DLI.
Choosing Unit System
Select metric (mol/m²/day) or imperial (mol/ft²/day) units for your results. Most scientific literature uses metric, but imperial is useful for some regions.

Usage Scenarios

  • Sunlight + LED: 10h at 250 μmol/m²/s + 6h at 600 μmol/m²/s
  • Metric vs. Imperial: 20 mol/m²/day ≈ 1.86 mol/ft²/day

Real-World Applications of DLI Calculations

  • Greenhouse Management
  • Indoor Farming
  • Crop Research
DLI calculations are essential for greenhouse managers, indoor farmers, and researchers. They help optimize lighting schedules, select appropriate grow lights, and ensure crops receive the right amount of light for each growth stage.
Greenhouse Lighting Optimization
By monitoring DLI, growers can adjust supplemental lighting to maintain optimal conditions year-round, regardless of natural sunlight fluctuations.
Crop-Specific DLI Targets
Different crops have unique DLI requirements. For example, lettuce thrives at 12-17 mol/m²/day, while tomatoes and cannabis require much higher DLI for maximum yield.
Research and Breeding
Researchers use DLI data to study plant responses to light, develop new cultivars, and improve agricultural practices.

Application Examples

  • Adjusting LEDs in winter to maintain 17 mol/m²/day for lettuce
  • Comparing DLI for tomatoes vs. flowers in the same greenhouse

Common Misconceptions and Correct Methods

  • Confusing PPFD and DLI
  • Ignoring Light Quality
  • Overestimating Light Duration
Many growers confuse PPFD (instantaneous light intensity) with DLI (total daily light). It's important to use both metrics for proper lighting management.
PPFD vs. DLI
PPFD tells you how much light is available at a moment, while DLI sums all light received in a day. High PPFD for a short time may result in low DLI, and vice versa.
Light Quality Matters
DLI measures quantity, not quality. The spectrum of light (wavelengths) also affects plant growth. Use DLI alongside spectrum analysis for best results.
Overestimating Light Duration
Total light hours per day should not exceed 24. Overestimating can lead to unrealistic DLI values and poor plant health.

Best Practice Guidelines

  • PPFD 1000 for 2 hours: DLI = 7.2 mol/m²/day (not enough for tomatoes)
  • 24h lighting: Not recommended for most crops

Mathematical Derivation and Examples

  • DLI Formula
  • Unit Conversions
  • Worked Examples
The DLI formula is: DLI = PPFD × hours × 0.0036. This converts μmol/m²/s and hours to mol/m²/day. For imperial units, divide the result by 10.764 to get mol/ft²/day.
Unit Conversion Details
1 mol = 1,000,000 μmol. 1 m² = 10.764 ft². To convert DLI from mol/m²/day to mol/ft²/day, divide by 10.764.
Worked Example
PPFD = 500 μmol/m²/s, Light = 14 hours: DLI = 500 × 14 × 0.0036 = 25.2 mol/m²/day. In ft²: 25.2 / 10.764 ≈ 2.34 mol/ft²/day.

Calculation Examples

  • Convert 30 mol/m²/day to ft²: 30 / 10.764 ≈ 2.79 mol/ft²/day
  • PPFD 200, 12h: DLI = 8.64 mol/m²/day