How to Select the Right LED Downlight: Size, Wattage, and IP Rating

Introduction

LED downlights are the go-to choice for modern UK homes and commercial spaces — energy-efficient, long-lasting, and available in a huge range of sizes and finishes. But with so many options, it's easy to order the wrong product. This guide covers everything you need to know to specify the right downlight first time.

Step 1: Get the Cutout Size Right

The cutout size is the hole diameter required in the ceiling. The most common sizes are:

• 70mm — compact downlights, ideal for low-depth ceilings
• 75mm — the most common standard size for UK residential
• 90mm — larger format, often used in commercial or feature lighting

Always check the cutout size on the product datasheet before ordering — it's not always the same as the overall bezel diameter. If you're replacing existing downlights, measure the existing hole rather than the old fitting.

Step 2: Choose the Right Wattage

LED wattage is much lower than the halogen equivalents they replace. A rough guide:

• 5–6W LED ≈ 50W halogen
• 7–8W LED ≈ 60–75W halogen
• 10–12W LED ≈ 100W halogen

For most domestic rooms, 5–6W per downlight is sufficient. In larger rooms or where task lighting is needed (kitchens, workshops), consider 7–8W. Check the lumen output (brightness) rather than wattage alone — aim for 400–600 lumens per downlight for general lighting.

Step 3: Select the Colour Temperature

Colour temperature is measured in Kelvin (K) and affects the mood of the space:

• 2700K (Warm White) — cosy, residential feel. Best for living rooms, bedrooms, hallways.
• 3000K (Warm White) — slightly crisper. Popular in kitchens and bathrooms.
• 4000K (Cool White) — clean, clinical. Ideal for offices, garages, utility rooms.
• 6500K (Daylight) — very bright and blue-toned. Used in workshops and display lighting.

For residential projects, 2700K–3000K is the most popular choice. Avoid mixing colour temperatures in the same room.

Step 4: Check the Beam Angle

Beam angle determines how wide the light spreads:

• 25–36° (Narrow/Spot) — focused beam, good for accent or task lighting.
• 60–90° (Wide) — broad spread, ideal for general room lighting.
• 100–120° (Very Wide) — maximum coverage, best for low ceilings.

For standard ceiling heights (2.4m), a 60–90° beam angle gives good coverage without harsh shadows.

Step 5: Understand IP Ratings for Wet Areas

IP (Ingress Protection) ratings are critical in bathrooms and kitchens. The two digits indicate protection against solids and liquids:

• IP20 — dry areas only (living rooms, bedrooms, hallways).
• IP44 — splash-proof. Suitable for bathroom Zone 2 (outside 0.6m of a shower or bath).
• IP65 — jet-proof. Required for bathroom Zone 1 (directly above a bath or shower tray) and outdoor soffits.
• IP67/IP68 — submersible. Used in specialist applications.

Under UK wiring regulations (BS 7671), using the wrong IP-rated fitting in a bathroom zone is a notifiable defect. Always check the zone before specifying.

Summary

Selecting the right LED downlight comes down to five key factors: cutout size, wattage/lumens, colour temperature, beam angle, and IP rating. Get these right and you'll have a professional, energy-efficient result that lasts for years.

Shop LED Downlights at APM

• All Downlights — integrated LED and GU10-compatible fittings, including fire-rated
• Fire Rated Downlights — IP65 rated for bathroom Zone 1 and timber floor applications
• GU10 LED Bulbs — warm white, cool white, and daylight, dimmable and non-dimmable
• Full LED Lighting Range — panels, strips, battens, and spotlights

Same-day collection from APM in Acton, West London. Next-day UK delivery on orders before 3pm.