Lighting Calculator

Size your lights and check PPFD and DLI against your stage targets. Then use spectrum, not just intensity: red:far-red, blue fraction, and crop-steering guidance to shape how the crop grows.

About this tool: PPFD, DLI, and choosing a light

🦬 BizonTip!

Feed this the fixture's real PPF from its PPFD map, not a headline "equivalent watts" number, and if you can, verify with a quantum meter at the canopy in several spots: bench edges routinely read half the center. Remember DLI, not instantaneous PPFD, is what grows the plant: if you can't reach the intensity you want, a longer photoperiod often gets you the same DLI (except on photoperiod-sensitive crops). Re-check as the canopy rises toward the light.

Coverage & Photoperiod

Area length ft

Area width ft

Photoperiod hours of light / day

Target stage

Custom DLI target

optional, overrides the stage band

Primary Fixtures

How is fixture output specified?

Number of fixtures

PPF per fixture µmol/s (from the spec sheet), not watts. For watts, switch to Watts × efficacy above.

Fixture size (W × L)

the lit footprint of one fixture

Beam angle wider spreads light, narrows the hot spot

Spectrum of these lights

Rough split from the spec sheet or channel settings; drives red:far-red, blue fraction, steering guidance, and the light map's tint. Percentages don't need to add to 100. Supplemental fixtures (far red, veg, bloom) are added on the light map with their own spectra, and Results blends them in by photon share.

Blue % · 400–500 nm

Green % · 500–600 nm

Red % · 600–700 nm

Far-red % · 700–800 nm

Light map

Results

Average PPFD assumes even coverage and no losses, so it reads high. Real canopy PPFD drops toward the edges.

Crop steering

What do you want the light to do?

Guidance grounded in photobiology (phytochrome, cryptochrome, UV photoreceptors), tagged by how well established it is. Crop-specific magnitudes vary, so treat it as a starting recipe and verify for your crop.

About this tool: PPFD, DLI, and choosing a light

Lux measures the wrong thing

Lux meters follow the human eye; photosynthesis counts photons from 400 to 700 nm, which is PPFD. No reliable conversion exists, it depends on the lamp.

DLI is what grows the plant

PPFD is a rate. Plants respond to the daily total.

DLI = PPFD × hours × 0.0036

Crop and stage	Target DLI
Seedlings and cuttings	6 to 12
Lettuce and leafy greens	12 to 17
Herbs	12 to 20
Tomatoes, peppers, cucumbers	20 to 30
High-light flowering crops	30 to 45

400 PPFD for 16 hours equals 640 for 10, except for photoperiod crops where you hold the hours and change intensity. Summer daylight runs 40 to 60.

Measure at the canopy

Canopy top, centre and corners. Bench edges routinely run half the centre.

More light stops helping, then hurts

Photosynthesis saturates, then bleaches. The ceiling rises with temperature and CO₂.

Spectrum, briefly

Blue compacts growth, red is most efficient per watt, far-red stretches, green penetrates deepest. Total light matters more than colour.

Compare fixtures on efficacy

Compare on µmol/J, not watts. Good current LEDs run 2.5 to 3.0.

Lighting Calculator