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Grow-light PPFD, DLI & hanging height Calculator

Grow-light PPFD, DLI & hanging-height calculator

Measured light, hours and fixture data → DLI, uniformity, interpolation and electricity cost.

Open full calculator · Calculation schema v2 · Sources checked 2026-10-28

Measured light & supplemental target

Targets are user-selected examples, not crop recommendations. Do not count lamp photons again if the ambient measurement already includes them.

Canopy grid
Separate 1–400 readings with commas, spaces or newlines. Use the same meter, plane, dimming and conditions.

Fixture estimate & electricity

Watts × photon efficacy gives PPF. Utilization and area convert it to an estimated canopy average. Watts or lumens alone cannot establish PPFD.

Two-height measurement interpolation

Enter comparable canopy means with identical footprint and dimming. Interpolate only between measured heights; check manufacturer clearance and leaf temperature separately.

JavaScript enables calculations and share links. The formulas and worked example below remain readable without it. Shared inputs stay in the URL fragment.

Enter your measurements, then select Calculate.

Your estimate

Measured-light DLI
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Supplemental DLI needed
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Required supplemental PPFD
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Required photoperiod at entered PPFD
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Grid mean / minimum / maximum
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Canopy uniformity (minimum / mean)
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Fixture PPF and estimated canopy PPFD
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Estimated fixture DLI
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Interpolated PPFD
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Electricity operating cost
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Assumptions and warnings appear after calculation.

Worksheet generation time appears after calculation.

Formula and worked example

DLI = 0.0036 × PPFD × hours. Example: 250 × 16 × 0.0036 = 14.4 mol/m²/day. Supplemental DLI = max(0, target − ambient). Required PPFD = supplemental DLI ÷ (0.0036 × hours); required hours = supplemental DLI ÷ (0.0036 × PPFD). More than 24 hours is infeasible.

PPF = watts × efficacy; estimated canopy average = PPF × utilization ÷ area. 100 W × 16 h × 30 days × $0.15/kWh costs $7.20. Two-height results use linear interpolation of supplied measurements, without extrapolation or a panel inverse-square assumption.

Purdue Extension: measuring DLI explains why one midday reading is not a daily measurement. Grid cells here have equal area. Read Kathy’s artificial light guide.

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