LEARN · FREE TOOL

PPFD grow-light calculator.

The short answer. PPFD is how much usable light reaches your plants, in µmol/m²/s. Herbs and salad leaves under LEDs want 200 to 400. Work it out as true watts × efficacy (µmol/J) ÷ grow area (m²), then multiply by hours × 0.0036 for the daily light integral (DLI).

50–150

houseplants

200–400

herbs and greens

400–600

fruiting crops

STEP BY STEP

Four numbers, one answer.

True wattage

Read the driver label or use a plug-in watt meter. Ignore "1000 W equivalent" on cheap listings.

Efficacy

Find PPE on the spec sheet: about 1.8 µmol/J for budget LEDs, 2.5 to 3.0 for good ones. If it isn’t listed, use 2.0.

Grow area

Width × depth of the canopy in metres. A 90 × 60 cm shelf is 0.54 m².

Multiply

(watts × µmol/J) ÷ m² gives PPFD. PPFD × hours × 0.0036 gives DLI.

HONEST ABOUT IT

What it can’t tell you.

THE LIMITS OF A CALCULATOR

It assumes light spreads evenly at a fixed height. Real light falls off with distance and is brighter in the middle, so measure at the canopy if it matters. Lux conversions are rough: a quantum (PAR) sensor is the accurate way.

SOURCES

Lux-to-PPFD factors: University of Maryland Extension. Crop targets: standard horticultural practice.

Every Metro cabinet ships with its lights already matched to its shelves. See Metro Solo

Want it done for you? Our cabinets come lit and tuned.

See the grow cabinets