DLI calculator
PPFD says how bright the light is right now. Daily light integral says how much light the plants got over the whole day, which is what growth responds to.
Common starting points
Growers and extension guides often quote daily light integrals in these ranges. Treat them as places to start: cultivar, CO₂ level, temperature and growth stage all move the useful number.
| Crop type | DLI, mol/m²/day |
|---|---|
| Leafy greens such as lettuce | 12 to 17 |
| Fruiting crops such as tomato and pepper | 20 to 30 |
| High-light flowering crops | 30 to 45 |
How it is calculated
PPFD counts photons per square metre per second. Multiply by the seconds of light in a day and convert micromoles to moles:
DLI = PPFD × hours × 3600 ÷ 1,000,000
And the other way round:
PPFD = DLI × 1,000,000 ÷ (hours × 3600)
PPFD should be measured at the canopy with a quantum (PAR) sensor; phone lux apps measure something else and cannot be converted reliably without knowing the light's spectrum.
GrowRoom's air pack includes a PAR sensor. Accurate PPFD needs a per-fixture conversion factor, checked against a quantum reference. The air sensor pack