How Far Should My Grow Light Be From My Plants?
This is the #1 question new indoor growers ask — and for good reason. Too close and you'll burn your canopy. Too far and your plants stretch toward the light, producing weak, leggy growth. The answer depends on two things: your light's intensity and your plant's growth stage.
The General Guidelines
| Growth Stage | Distance from Canopy | Why |
|---|---|---|
| Seedling | 24–36 inches | Young plants are fragile and need gentle light |
| Vegetative | 18–24 inches | More light drives leaf growth without stress |
| Flowering | 12–18 inches | Maximum intensity for bud development |
These ranges work for most modern LED grow lights in the 200–800W range. But they're starting points, not gospel.
Why "It Depends" Is the Real Answer
A 200W light at 12 inches delivers far less intensity than a 600W light at the same distance. What actually matters is the PPFD (Photosynthetic Photon Flux Density) hitting your canopy — measured in µmol/m²/s.
- Seedlings: 200–400 µmol/m²/s
- Veg: 400–600 µmol/m²/s
- Flower: 600–900 µmol/m²/s (up to 1,000+ with CO2 supplementation)
Higher-wattage lights with better efficacy (measured in µmol/J) produce more photons per watt — meaning they need to be mounted higher to avoid overwhelming your plants.
Signs You're Too Close
- Bleaching or yellowing on the top leaves (closest to light)
- Leaf edges curling upward ("taco-ing")
- Brown, crispy tips on new growth
Signs You're Too Far
- Excessive stretching between nodes
- Thin, weak stems
- Lower leaves reaching upward
💡 Pro tip: If your light is dimmable, start at 50–75% intensity and raise it gradually over a week. This is safer than adjusting height alone — and most of the lights in our dataset support 0–10V dimming.
Use Your Light's Specs
Many manufacturers publish PPFD maps at specific mounting heights. Check the product page or PDF spec sheet for your light. Our comparison tool shows the recommended mounting heights from manufacturer data when available.
The Bottom Line
Start with the general guidelines above, watch your plants for stress signals, and adjust. Every grow room is different — ambient temperature, airflow, and reflective walls all affect how your plants respond to light intensity.
Use our Grow Cost Calculator to see how your light's wattage translates to real electricity costs across a full grow cycle.