PPFD Cheat Sheet: Light Targets for Every Indoor Food Crop

Affiliate disclosure. Our recommendations are independent. We earn a small commission when you buy through links on this page — at no extra cost to you. Read our methodology.

PPFD (Photosynthetic Photon Flux Density) is how you measure whether your grow light is actually bright enough for your plants. It’s expressed in µmol/m²/s — the number of usable light photons hitting a square meter of plant canopy per second.

The problem: almost all PPFD guidance on the internet is calibrated for cannabis, which needs 800-1500 PPFD for flowering. Food crops need dramatically less. If you’re growing tomatoes, peppers, lettuce, herbs, strawberries, or microgreens indoors and you’ve been following cannabis-grade PPFD targets, you’re probably overspending on lights and electricity by 2-4x.

This reference table gives you the actual PPFD targets for every common indoor food crop, plus the LED wattage and daily photoperiod to hit those targets in common tent sizes. Bookmark it. Print it. Tape it to your tent.

The Table

Key:

• SF1000 = Spider Farmer SF1000, 100W, ~$149
• SF2000 = Spider Farmer SF2000, 200W, ~$249
• Barrina T5 = Barrina T5 LED strip lights, 40W per 4-pack, ~$30-60
• SANSI 24W = SANSI screw-in grow bulb, ~$25
• DLI = Daily Light Integral (total photons per day = PPFD × photoperiod hours × 0.0036)

Cannabis flowering is included at the bottom for reference so you can see exactly how over-specced cannabis PPFD targets are for food crops. An 800 PPFD cannabis target is roughly 2-4x the PPFD any food crop in this table needs. That’s why cannabis-tilted LED recommendations push 400-600W panels — and why food growers should ignore those recommendations.

How to Use This Table

Step 1 — Find your crop

Look up the crop you’re growing (or will grow) in the left column. Note the PPFD target range and the recommended photoperiod.

Step 2 — Find your tent size

The “LED for 2x2” and “LED for 2x4” columns give you the recommended LED model and the approximate dimming level to hit the right PPFD for that crop in that tent size. These are based on the Spider Farmer SF series because it’s the best $/PPFD in the Samsung-diode class and available in all four target markets.

Step 3 — Adjust for height

The PPFD numbers in this table assume a standard hanging height of 18 inches above the canopy for panel lights and 6-12 inches above the canopy for strip lights. If you hang your light higher, PPFD drops (roughly inverse-square — double the distance, quarter the PPFD). If you hang lower, PPFD increases. Use the dimming knob to compensate.

Step 4 — Adjust during growth

Most crops don’t need the same PPFD throughout their lifecycle. Seedlings want 100-200 PPFD. Vegetative growth ramps up. Fruiting stage peaks. Use the dimming knob to ramp light intensity as plants mature — don’t run full power from seedling stage (it wastes electricity and can stress young plants).

What Is DLI and Why Does It Matter?

DLI (Daily Light Integral) is the total amount of light a plant receives per day, measured in mol/m²/day. It’s calculated as:

DLI = PPFD × hours of light × 0.0036

DLI is actually a more useful metric than PPFD alone because it accounts for photoperiod — a plant getting 300 PPFD for 16 hours receives a higher DLI (17.3) than one getting 400 PPFD for 12 hours (17.3). Same DLI, different experience.

For food growers, the practical implication is: if your light isn’t bright enough to hit the PPFD target, you can partially compensate by running a longer photoperiod (more hours per day). Lettuce at 200 PPFD for 16 hours gets the same DLI as lettuce at 300 PPFD for 10.7 hours. This means a cheaper, dimmer LED can produce equivalent results if you run it longer.

The limit: most edible crops need a dark period of at least 6-8 hours for proper metabolic function. Running lights 24/7 to compensate for a dim LED is counterproductive — plants need darkness for respiration and growth hormone regulation. Maximum practical photoperiod for food crops is 16-18 hours.

Common Mistakes Food Growers Make with PPFD

Mistake 1: Following cannabis PPFD targets

Cannabis flowering needs 800-1500 PPFD. Food crops max out at 900 PPFD (tomatoes at peak fruiting) and most need only 200-500. A cannabis-grade 450W LED on a 2x4 tent of lettuce delivers roughly 3-4x the light the lettuce can actually use. The excess light doesn’t hurt the lettuce (it just doesn’t use it) — but you’re paying for 3-4x the electricity and 3-4x the hardware cost.

Mistake 2: Not dimming

Most LEDs in this guide have a dimming knob. Use it. A $249 Spider Farmer SF2000 dimmed to 40% for lettuce delivers perfect results at lower electricity than an SF1000 at full power. The dimming knob is the most underused feature on any grow light and it’s the feature that makes a single LED versatile across multiple crops.

Mistake 3: Measuring PPFD at the wall instead of at the canopy

PPFD drops dramatically with distance. The manufacturer spec for “1100 PPFD” on an SF2000 is measured at 18 inches. At 24 inches it’s more like 700 PPFD. At 36 inches it’s more like 350. The number that matters is PPFD at the canopy height where your plants actually are, not the number printed on the box.

Mistake 4: Ignoring spectrum

All the PPFD in the world doesn’t help if the spectrum is wrong. Full-spectrum white LEDs (like the Samsung LM301H used in most quantum boards) are a good default for all food crops. For fruiting vegetables specifically, warm-yellow spectrum produces significantly better fruit set — see the Barrina warm-yellow tomato research (57% more flowers, 93% more fruit vs standard red-blue).

Frequently Asked Questions

Is more PPFD always better?

No. Each crop has an optimal range — above that range, additional PPFD produces diminishing returns and can even stress plants. Lettuce exposed to 800+ PPFD will bolt (go to seed prematurely), which ruins the harvest. Basil exposed to sustained 1000+ PPFD can develop leaf burn. More light is not always better for food crops.

Do I need a PAR meter to measure PPFD at home?

A dedicated PAR meter (like the Apogee MQ-500, ~$500) is the gold standard but wildly overkill for home use. For food growers, the PPFD spec from the manufacturer + the dimming knob + the tent size is enough information to hit the right range. If you want to verify, some smartphone apps (like Photone) can estimate PPFD from the phone camera — not lab-accurate but close enough for home growing.

Does tent color affect PPFD?

Yes. Reflective Mylar-lined tents bounce unused light back to the plant canopy, effectively increasing PPFD by 20-40% vs a non-reflective surface. This is why all the tents in our grow tent guide use reflective Mylar lining — it’s free PPFD.

What if I’m growing multiple crops with different PPFD needs in the same tent?

Position high-PPFD crops (tomatoes, peppers) directly under the center of the LED panel where intensity is highest, and low-PPFD crops (lettuce, herbs) at the edges where intensity drops off. Alternatively, use the dimming knob to find a middle-ground PPFD that works for both — 400-500 PPFD is a reasonable compromise for a mixed tent with herbs and tomatoes.

Is this table accurate for vertical hydroponic towers too?

Mostly yes. Vertical towers with built-in lighting (like Lettuce Grow Glow Rings or Gardyn’s integrated LEDs) deliver side-mounted light at each planting level, which changes the PPFD geometry vs a top-mounted panel in a tent. The crop-level PPFD targets in this table are the same regardless of whether the light comes from above or from the side — but the LED wattage recommendations are specific to tent setups with top-mounted panels.

Bottom Line

The single most important takeaway from this table: food crops need dramatically less light than cannabis content leads you to believe. Lettuce at 200-400 PPFD, herbs at 300-500, tomatoes at 600-900. That translates to 100-200W of LED for a 2x4 tent — roughly half to a third of what cannabis-tilted guides recommend.

Bookmark this page, reference it when shopping for lights, and use the dimming knob to match your LED output to what your actual crops need. Your electricity bill will thank you.

For the LED buying guide that matches these PPFD targets to specific products, see our Best LED Grow Light for Indoor Vegetables companion guide.

Sources. PPFD and DLI targets in this table are synthesized from: Ohio State University Extension (HYG-1437), University of Florida IFAS (HS1422), Cornell University CEA guidelines, Purdue University Extension, and manufacturer photometry data from Spider Farmer, AC Infinity, and Barrina. Where sources disagree on exact ranges, we’ve used the conservative (lower-PPFD) end to avoid over-speccing for home growers. Read our full methodology.

Affiliate disclosure (full). Read our full affiliate policy.

Related guides:

• Best LED Grow Light for Indoor Vegetables in 2026 →
• Best LED Spectrum for Indoor Tomatoes →
• Best 2x4 Grow Tent Setup for Indoor Vegetables →
• Best Hydroponic Nutrients for Indoor Food Growing →
• The Masterblend Calculator →