Scenario 1
An ambient DLI of 8 and sourced minimum of 12 leave a 4 mol/m²/day gap. The numbers demonstrate arithmetic only; they are not a crop target, fixture promise, HVAC selection, or safe operating limit.
Supplemental DLI Gap Calculator
Created by: Sophia Bennett
Last updated:
Compare measured ambient DLI with an authority-entered target and calculate supplemental hours or PPFD from measured fixture output, transmission, and dimming.
Supplemental DLI Gap Calculator
Hydroponics & Indoor GrowingSolve a measured ambient-light gap using authority-entered DLI and measured canopy PPFD—without selecting a target or photoperiod.
No crop target is prescribed. Never infer PPFD from watts/lux or extend beyond crop-authority photoperiod constraints.
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What is a Supplemental DLI Gap Calculator?
A Supplemental DLI Gap Calculator is a controlled-environment measurement worksheet that calculates the gap between measured ambient DLI and an authority-entered target, then solves supplemental hours or average PPFD from measured fixture output, transmission, dimming, and a maximum window. It keeps source labels, assumptions, intermediate values, and exceptions visible so the record can be audited before anyone changes lighting or environmental equipment.
Indoor crop conditions vary across space and time. A fixture map applies only at its tested height and configuration. A quantum-sensor point cannot stand in for an entire canopy. Natural DLI changes by day and season. Air temperature does not equal leaf temperature, and relative humidity alone does not describe vapor-pressure deficit. Likewise, reservoir top-up is not automatically transpiration because drains, leaks, harvest water, cleaning, storage change, and recovery may also be present.
It does not select a crop target, exceed crop photoperiod constraints, infer PPFD from watts or lux, or replace the canonical generic DLI converter. This narrow scope prevents a tidy arithmetic result from being mistaken for crop physiology, equipment approval, or building design. Purdue Extension describes DLI as accumulated photosynthetic light and notes that light-source-dependent conversions matter. Cornell CEA resources emphasize controlled measurement, while DOE dehumidifier information ties product ratings to standardized test procedures.
Use the tool as a dated observation: identify the crop/stage source and exact equipment state, measure a representative grid or interval, calculate without changing labels, inspect exceptions, make only a controlled change under the applicable plan, and repeat the same measurement. Escalate electrical, thermal, condensation, mold, drainage, fire, worker-safety, or food-safety concerns to qualified people.
How the calculation works
Measured fixture PPFD is reduced by entered transmission and dimming. Supplemental DLI equals effective PPFD times hours times 0.0036. A surplus creates zero required supplemental time. Inputs remain in explicit physical units, invalid ranges are rejected, and display rounding does not change the underlying calculation. Comparisons use the user-entered source range; they do not generate a biological threshold.
effective PPFD = measured PPFD × transmission × dimming
supplemental DLI = effective PPFD × hours × 0.0036
required hours = DLI gap ÷ (effective PPFD × 0.0036)
Charts reveal scenario or measurement differences, while the table preserves the individual records that produced each summary. A favourable average never erases a missing point, low location, out-of-range interval, water-balance residual, or rating-condition mismatch.
Example records
Scenario 2
At a measured effective 200 µmol/m²/s, that gap requires about 5.56 hours before crop photoperiod constraints are considered. The numbers demonstrate arithmetic only; they are not a crop target, fixture promise, HVAC selection, or safe operating limit.
Scenario 3
If ambient DLI already exceeds the entered range, the arithmetic gap is zero; the tool does not recommend additional light. The numbers demonstrate arithmetic only; they are not a crop target, fixture promise, HVAC selection, or safe operating limit.
Common applications
These records support commissioning, comparison, and troubleshooting when their sources and conditions are retained.
- Plan a measured seasonal light gap.
- Compare dimming scenarios.
- Record glazing or shade transmission.
- Solve hours from measured canopy PPFD.
- Solve required PPFD inside an allowed window.
- Document a remaining shortfall without extending photoperiod automatically.
Measurement and verification tips
- Measure ambient DLI at crop height.
- Cite crop and stage target source.
- Measure fixture average PPFD over the canopy.
- Respect crop-authority photoperiod constraints.
- Verify achieved DLI with logging sensors.
Lighting and climate equipment can create electrical, heat, fire, condensation, refrigerant, drainage, and worker hazards. Use listed equipment as instructed and obtain qualified design and commissioning where consequences are material.
Frequently asked questions
What does the Supplemental DLI Gap Calculator calculate?
It calculates the gap between measured ambient DLI and an authority-entered target, then solves supplemental hours or average PPFD from measured fixture output, transmission, dimming, and a maximum window. Results describe only the entered geometry, measurements, time window, or equipment rating. It does not select a crop target, exceed crop photoperiod constraints, infer PPFD from watts or lux, or replace the canonical generic DLI converter.
Are the example targets or values crop recommendations?
No. Defaults demonstrate the interface only. Replace them with a current crop-and-stage authority, an exact fixture or equipment document, calibrated measurements, and a clearly identified time and sensor location. The calculator never selects a universal DLI, PPFD, VPD, photoperiod, humidity, or dehumidifier target.
Can watts, lux, or one PPFD reading describe canopy light?
No. Watts are electrical input, lux is human-vision weighted, and one PPFD point does not show spatial uniformity or daily accumulation. Use a suitable calibrated quantum sensor, a documented grid and fixture state, and the exact manufacturer map at the installed height and configuration.
Why are measured and estimated leaf temperatures kept distinct?
Leaf temperature materially changes leaf VPD. An estimate based on air temperature is not equivalent to an infrared or contact measurement and may miss spatial and time variation. Keep the source label visible, retain sensor details, and avoid turning either value into a universal irrigation or disease-control instruction.
Does the moisture result size HVAC or prevent mold?
No. A water balance is only one input to latent-load analysis. Ventilation, infiltration, envelopes, surface temperatures, sensible loads, controls, equipment performance at actual temperature and RH, drainage, refrigerants, and worker exposure require qualified HVAC and building review.
What should be measured next?
Repeat the grid or time series under the same documented equipment state, verify sensor calibration and placement, compare equipment output at the applicable rating condition, and retain the before-and-after record. Investigate unexplained water, light, or climate differences instead of assigning them automatically to plant demand.
Can these worksheets certify a commercial crop facility?
No. They do not certify crop health, food safety, worker safety, electrical capacity, fire protection, structure, HVAC, drainage, sanitation, or code compliance. Follow current manufacturer instructions, extension and crop-authority guidance, and applicable qualified professionals and regulators.
Sources and references
- Purdue Extension — Measuring Daily Light Integral in a Greenhouse (HO-238-W) (accessed 12 August 2026).
- Cornell Controlled Environment Agriculture (accessed 12 August 2026).
- University of Minnesota Extension — Small-scale hydroponics (accessed 12 August 2026).
- U.S. Department of Energy — Consumer Dehumidifiers (accessed 12 August 2026).
- The exact current quantum-sensor, fixture, environmental sensor, controller, dehumidifier, drainage, and crop-authority documents used for the entered scenario.