How Far Should Grow Lights Be From Plants?
Written by Matt W on 23rd Jun 2026.
Most LED grow lights sit 30 to 60cm above the plant canopy, but the exact height changes with the light's power and the growth stage. Seedlings want a gentler dose, so hang the light higher, around 60 to 90cm. Lower it through flowering, down to 25 to 45cm. Watch the top leaves: bleaching means too close, while stretched, leggy stems mean too far. A dimmer lets you set intensity without shifting the light.
Key takeaways
- A safe LED starting height is 30 to 60cm above the canopy.
- Hang the light higher for seedlings, around 60 to 90cm, to soften the dose.
- Lower it as plants grow, down to 25 to 45cm for flowering.
- Bleached or curled top leaves mean too close; stretched stems mean too far.
- Higher-wattage fixtures need to hang further away than small ones.
- A dimmer adjusts intensity without moving the light, which is easier on young plants.
Grower's note: The figures below are a starting point, not a law. Every fixture is different, so set the height, then read the plants for a week. If the tops pale, raise it. If the plants stretch and reach, lower it. The plants tell you faster than any chart.
- Matt W, Hydroponics UK
How far should grow lights be from plants?
Most LED grow lights belong 30 to 60cm above the canopy, but power and growth stage move that figure. A small bar light can sit close. A high-output fixture pushes far more light, so it has to hang higher to spread that intensity safely. The chart below gives sensible starting heights and the light level, measured as PPFD, that each stage wants.
| Growth stage | Height above canopy | Light level (PPFD) |
|---|---|---|
| Seedlings and clones | 60 to 90 cm | 200 to 300 |
| Vegetative growth | 40 to 60 cm | 400 to 600 |
| Early flower | 30 to 45 cm | 600 to 800 |
| Late flower or fruiting | 25 to 40 cm | 800 to 900 |
Always measure to the top of the plants, not the floor, and raise the light as the canopy climbs. Check the manufacturer's own chart too. A maker who tests their fixtures publishes exact heights per model. Our guide to choosing an LED explains how.
How does hanging height change by growth stage?
Young plants want less light, mature plants want more. A seedling has a tiny root system and little leaf area, so a strong light close up just scorches it. Start high and gentle. As the plant fills out through its vegetative stage, drop the light to feed the bigger canopy. By flowering or fruiting, the plant takes the most intense light it will ever need. The fixture then sits at its lowest safe point.
This is where a dimmable light earns its place. You turn the intensity down for seedlings and up for flower. No climbing into the tent to move the fixture. It is gentler on the plants and far easier on you. Our beginner's guide to hydroponics covers how light fits the wider setup.
Shop the Sanlight FLEX II 20 bar →
How do I know if my grow light is too close or too far?
The plants show you within days. Too close, and the top leaves bleach pale, curl at the edges like a taco, and growth stalls. Too far, and plants stretch upward with long, thin stems and wide gaps between leaves. A healthy distance gives tight spacing, deep green leaves and steady growth.
Do not trust the old hand test from HPS days. LED fixtures run cool to the touch but still deliver intense light. Your hand feels nothing while the plant gets too much. Read the leaves instead, or use a PAR meter for an exact figure. Adjust in small steps of 5 to 10cm and wait a few days between changes.
How high should a Sanlight grow light hang?
It depends on the fixture's output. A modular bar runs cooler and lower-powered, so it sits close. A large all-in-one panel pushes far more light and hangs higher. The table shows starting heights for three popular Sanlight options we stock.
| Fixture | Type | Starting height | Price |
|---|---|---|---|
| Sanlight FLEX II 20 bar | Modular bar | From 15 cm | £84 |
| Sanlight EVO 3-100 | All-in-one fixture | From 30 cm | £455 |
| Sanlight EVO 5-150 | High-output fixture | From 45 cm | £735 |
Matt's Pick: Sanlight EVO 3-100
Best for: a 1m² tent or cabinet with low headroom
Why we rate it: the 90° lens spreads light evenly from close range, so it suits low UK ceilings. Add the optional dimmer and you set intensity without moving the fixture.
Price: £455
Watch out: light burn on a new fixture. Modern LEDs are powerful, and growers used to old lamps often hang them far too close. If the newest leaves bleach or curl within a week, raise the light 10cm. Give the plants a few days to recover.
We like the Sanlight range for distance because of the optional magnetic dimmer. Most growers fuss over height when intensity is the real lever. With a dimmer you keep the fixture at a steady, safe height and turn the power up through the grow. It is the simplest way to avoid light burn on young plants.
- Matt W, Hydroponics UK
Frequently asked questions
How far should an LED grow light be from seedlings?
Hang it 60 to 90cm above seedlings. Young plants burn easily under strong light, so start high. Lower the light gradually as they grow stronger and fill out.
Can an LED grow light be too close to plants?
Yes, too close bleaches and curls the top leaves. LEDs feel cool but still deliver intense light. If the newest growth pales or tacos, raise the fixture by 10cm.
How do I measure the distance to my plants?
Measure from the light to the top of the canopy. Not the floor or the pots. Raise the light as the plants grow to hold that gap steady.
Is a dimmer better than moving the light?
For most growers, yes. A dimmer changes intensity without climbing into the tent. Keep the fixture at a safe height and dial the power up through the grow.
Does LED hang closer than HPS?
Usually yes, because LEDs run far cooler. An HPS lamp radiates heat that forces extra distance. For the full comparison, see our LED running-costs guide.
Why are my plants stretching under the light?
The light is too far away or too weak. Plants stretch and thin out reaching for light. Lower the fixture, turn up a dimmer, or fit a stronger light.