Best Grow Lights for Every Tent Size (UK Guide 2025)

Introduction

Choosing the best grow lights for every tent size is essential if you wish to achieve strong, healthy plants and efficient energy use.
Too little light and growth stalls; too much and you risk burning or wasting electricity.

This guide covers the best LED wattage and light spacing for popular UK grow tent sizes — from small 60 × 60 cm (2 × 2 ft) setups to full grow rooms over 9 metres long.
We’ll also explain how to arrange multiple fixtures in larger spaces for even light coverage and better yields.

Not quite what you’re looking for? Take a look at our Grow Lights UK – Complete Resource Hub for a full overview of light types, setup tips, and running costs.

Affiliate notice: Some links are affiliate links. As an Amazon Associate, HomeGrower may earn from qualifying purchases at no extra cost to you.

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Grow Light Coverage & Wattage Chart

Grow Tent / Room Size	Approx. Area	Total LED Power (W)	Target PPFD (µmol·m⁻²·s⁻¹)	Example Fixture	Notes
2 × 2 ft (60 × 60 cm)	0.37 m²	100–150 W	400–600	Spider Farmer SF1000	Ideal for seedlings, herbs, and leafy greens.
3 × 3 ft (90 × 90 cm)	0.84 m²	200–300 W	600–900	AC Infinity IONBoard S22	Suited for 2–4 compact plants; easy heat control.
4 × 4 ft (120 × 120 cm)	1.44 m²	400–600 W	900–1000	Mars Hydro FC3000	Popular “full grow” footprint; excellent balance of coverage and power.
5 × 5 ft (150 × 150 cm)	2.25 m²	600–800 W	≈1000	AC Infinity IONBoard S44	Step up extraction (≥8″) and airflow for best results.
8 × 4 ft (240 × 120 cm)	2.88 m²	600–800 W	900–1000	Spider Farmer SE3000	Two fixtures side-by-side with 10–20% overlap in the centre for even canopy coverage.
10 × 5 ft (300 × 150 cm)	4.50 m²	800–1200 W	900–1000	Mars Hydro FC4800	Run two for veg, add a third for dense flowering canopy.
12 × 8 ft (360 × 240 cm)	8.64 m²	1300–1800 W	900–1000	Spider Farmer SE5000	Arrange two fixtures in a 2×2 grid for balanced PPFD across the canopy.
10 × 10 ft (300 × 300 cm)	9.00 m²	1600–2400 W	900–1000	Spider Farmer SE7000	Use two fixtures for general growth; add a third for high-light crops or dense canopies.
20 × 10 ft (600 × 300 cm)	18.0 m²	2400–3200 W	900–1000	Mars Hydro FC-E8000	Commercial layout; space fixtures evenly with strong airflow and dual extraction zones.
30 × 15 ft (900 × 450 cm)	41.9 m²	4800–6400 W	900–1000	AC Infinity IONFrame EVO8	Divide into lighting zones on separate timers for optimal efficiency and easy maintenance.

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How to Calculate Grow Light Coverage & Power Needs

Getting the right lighting setup is the foundation of healthy indoor growth. The best grow lights for every tent size deliver enough intensity to drive photosynthesis without wasting energy or overheating your plants. To achieve this balance, you’ll need to calculate coverage and wattage based on both the size of your grow tent and the light efficiency (PPFD) of your LEDs.

For modern, high-efficiency LEDs, aim for 30–40 watts per square foot (≈320–430 W per m²) of canopy area. This range provides a target PPFD (photosynthetic photon flux density) of around 600–1,000 µmol·m⁻²·s⁻¹, which suits most edible crops, herbs, and flowering plants.

To calculate your total lighting power:

1. Measure your tent’s footprint – for example, a 4×4 ft (1.44 m²) space.
2. Multiply by 35 watts per square foot (or ~375 W per m²).
   • A 4×4 tent: 16 sq ft × 35 W = 560 W total LED draw.
3. Match the result to real fixtures – for instance, one 600 W LED or two 300 W panels evenly spaced.

Each tent size has its own optimal light intensity and fixture type. The table below provides a quick reference for wattage, PPFD, and suggested models covering both compact and multi-light grow setups.

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How to Choose the Right Grow Light

1. Match Coverage to Tent Size – The “flowering coverage” rating in LED specs should match your tent dimensions.
2. Use Reflective Surfaces – Tents naturally reflect light back into the canopy; open rooms may require white or mylar-coated walls.
3. Mind the Height – Keep LEDs 25–45 cm (10–18 in) above the canopy depending on brightness and growth stage.
4. Watch Efficiency – Look for lights rated 2.5–3.0 µmol/J or higher for the best results per watt.

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Multi-Light Layouts & Spacing for Large Tents

When your grow space exceeds about 1.5 m (5 ft) in either direction, multiple LEDs are more effective than one large unit. They distribute light evenly and prevent edge dimming.

General spacing rules:

• Overlap coverage zones by 10–20%.
• Keep edge lights 20–30 cm (8–12 in) from tent walls.
• Row spacing for long tents (8×4 ft / 240×120 cm): two fixtures about 60–75 cm apart centre-to-centre.
• Grid spacing for rooms (12×8 ft / 360×240 cm): four lights in a 2×2 layout spaced around 120–150 cm apart.
• Height: 45–60 cm (18–24 in) in vegetative growth, 25–40 cm (10–16 in) in flowering.
• Airflow: match fan size to total wattage (6″ for ≤600 W, 8″ for 600–1200 W, 10″+ for 1200+ W).

Example setups:

• 240×120 cm (8×4 ft): 2 lights, each 300–400 W, ~65 cm apart.
• 300×150 cm (10×5 ft): 3 lights — one central, two flanking, ~1 m apart.
• 360×240 cm (12×8 ft): 4 lights in a 2×2 grid, ~130 cm apart.
• 300×300 cm (10×10 ft): 6 lights in a 2×3 grid for dense canopies.

Pro tip: Use a PAR meter or app to check light uniformity — readings within ±15% across the canopy are ideal.

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Conclusion

Whether you’re lighting a small 2×2 tent or a full 10×10 grow room, following these recommendations will help you choose the best grow lights for every tent size and get consistent yields year-round.

Use efficient LEDs, monitor canopy PPFD, and plan light spacing for even coverage — your plants will reward you with healthier growth and higher yields.

For expert advice on grow lights and other topics related to growing and gardening, check out the Royal Horticultural Society’s website.

Looking for more indoor gardening tips? Visit HomeGrower to explore our full range of self-sufficiency and gardening guides.

Further reading:

• Best Indoor Grow Lights UK 2025
• Best UK Grow Room Setups 2025
• How to Set Up Grow Lights Indoors