What is the ideal PPFD for indoor growing?

Ideal PPFD varies by plant and growth stage. Seedlings and clones need 100–300 µmol/m²/s. Vegetative growth thrives at 400–600 µmol/m²/s. Flowering and fruiting plants need 600–900 µmol/m²/s. Lettuce and herbs grow well at 150–350 µmol/m²/s. Tomatoes and peppers need 400–700 µmol/m²/s.

What is a good DLI for indoor plants?

A good DLI for most indoor plants is 20–40 mol/m²/day depending on the crop. Leafy greens and herbs do well at 12–20 mol/m²/day. Vegetative plants need 20–35 mol/m²/day. Flowering and fruiting crops need 25–40 mol/m²/day. Use the PPFD and DLI calculator above to find your exact daily light integral based on your light intensity and photoperiod.

How do I calculate DLI from PPFD?

DLI = PPFD × photoperiod hours × 3600 ÷ 1,000,000. For example, a PPFD of 500 µmol/m²/s running 18 hours gives a DLI of 500 × 18 × 3600 ÷ 1,000,000 = 32.4 mol/m²/day. Use our calculator above to compute this instantly for any combination of PPFD and photoperiod.

What is the best grow light for high PPFD in Canada?

For high PPFD in Canadian grow tents, the Mars Hydro FC-3000 and FC-4800 are top picks, delivering over 1,200 µmol/m²/s at canopy level in a 4×4 ft tent. Spider Farmer's SE series lights using Samsung LM301B diodes are also excellent and ship reliably to Canada. Both brands offer full-spectrum output optimised for both vegetative and flowering stages.

How many hours of light do indoor plants need?

Most indoor plants need 16–18 hours of light per day during vegetative growth and 12 hours during flowering. Clones and seedlings do well at 18 hours. Lettuce and herbs can run 16–20 hours. Autoflowering plants grow on 18–20 hours throughout their entire lifecycle. Use a programmable timer or smart controller to maintain a consistent photoperiod — inconsistent light schedules stress plants and reduce yields.

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PPFD & DLI Calculator

Calculate your grow light's PPFD and Daily Light Integral — and find out if your plants are getting enough light to thrive.

📊 PPFD & DLI Targets by Plant / Stage

Plant / Stage	PPFD Target	DLI Target	Photoperiod
🌱 Seedling / Clone	100–300	6–12 mol/m²/d	18 hrs
🌿 Vegetative	400–600	20–35 mol/m²/d	18 hrs
🌸 Flower / Fruiting	600–900	25–40 mol/m²/d	12 hrs
🍅 Tomatoes / Peppers	400–700	22–35 mol/m²/d	16 hrs
🥬 Lettuce / Greens	150–300	12–17 mol/m²/d	16 hrs
🌿 Herbs / Microgreens	150–350	10–20 mol/m²/d	16 hrs

I know my PPFD I know my DLI

Your PPFD (µmol/m²/s) Find this on your light's PPFD map — or measure it with a PAR meter at canopy height.

Photoperiod (hours of light/day)

Plant / Growth Stage

Common Questions

What is PPFD and how is it different from lumens or watts?

PPFD (Photosynthetic Photon Flux Density) measures the number of photons in the 400–700nm range hitting one square metre of plant canopy every second, expressed in µmol/m²/s. Lumens measure light brightness as perceived by the human eye — not useful for plants. Watts measure energy consumption, not light output. PPFD is the only measurement that tells you how much usable light your plants actually receive. Always ask for a manufacturer's PPFD map before buying a grow light.

What is DLI and why do indoor growers track it?

DLI (Daily Light Integral) is the total amount of photosynthetically active light delivered to your plants over a full day — it's PPFD multiplied by your photoperiod in seconds, divided by one million. DLI lets you compare lighting setups regardless of photoperiod length. A plant needs a minimum DLI to grow well, and you can hit that target with either a bright light on a short schedule or a dimmer light running longer. Vegetative plants typically need 20–35 mol/m²/day; flowering plants need 25–40 mol/m²/day.

How do I find out my actual PPFD without a PAR meter?

The most accurate way is a dedicated quantum PAR meter (like the Apogee MQ-500) placed at canopy height. A cheaper option is the Photone app on a modern iPhone — it uses your camera sensor to estimate PPFD and is reasonably accurate for LED lights. Manufacturer PPFD maps are useful as a starting point but represent ideal centre-point measurements — real-world edge readings are typically 30–50% lower. Never rely on wattage or lumen ratings to estimate your actual PPFD.

What PPFD do tomatoes and peppers need indoors in Canada?

Tomatoes and peppers are high-light crops that thrive at 400–700 µmol/m²/s with a DLI of 22–35 mol/m²/day. Run them on a 16-hour photoperiod indoors. In Canada, supplemental grow lighting for tomatoes and peppers is almost essential from October through March when natural light is insufficient even on sunny days. A 300W LED in a 3×3 tent will handle 2–4 plants at productive PPFD levels year-round.

Can too much PPFD hurt my plants?

Yes — light burn is real and can permanently damage your plants. Symptoms include bleached or yellowing upper leaves closest to the light, upward leaf curl, and stunted growth at shoot tips. Most plants max out their photosynthetic capacity at around 1,000–1,500 µmol/m²/s — beyond that you're wasting electricity and risking damage. If your PPFD is too high, raise the light, reduce your dimmer, or shorten your photoperiod before increasing CO₂ supplementation (which raises the ceiling).