Lighting Size Guide

How to Calculate the Right Size Light Fixture for a Room

Lighting is a key design and functional element. Choosing the right size ensures balance and adequate illumination. This guide provides professional formulas (in metric units) and room-specific tips for chandeliers, pendants, flush mounts, sconces, and more.

Note: UK standard ceiling heights are 2.4-2.7m; for electrical work, hire a qualified electrician to comply with Part P regulations. To view the complete page: click here

1. General Formula for Fixture Diameter

  • Measure room length and width in metres.
  • Add them and multiply by 10 for ideal diameter in cm (approximate rule of thumb).
  • Example: For a 3.7m x 4.3m room, 3.7 + 4.3 = 8; 8 x 10 = 80cm diameter.

2. Height of a Light Fixture

  • Measure ceiling height in metres.
  • Multiply by 20-25 for fixture height in cm.
  • Example: For a 3m ceiling, fixture height = 60-75cm.

3. Hanging Height of Fixtures

  • Above dining table or kitchen island: 80-90cm above surface.
  • General clearance: At least 2.1m from floor to fixture bottom.
  • Multiple pendants: Each ≈1/4 the surface length; space 60-90cm apart.

4. Sizing for Portable and Wall Fixtures

  • Table/Desk Lamps: Total height 50-70cm (match to surface height, e.g., ≈ nightstand for bedside). Shade height 1/2-2/3 lamp height; width 2x base for balance. Position at eye level when seated to avoid glare; desk lamps should illuminate work area without shadows (arm adjustable ideal).
  • Floor Lamps: Overall height 145-160cm. Shade 30-40% of base height; ensure ≥8cm bulb clearance. Place in corners or beside seating with shade base at seated eye level.
  • Wall Sconces: Width 10-25cm; height from floor 152-170cm (or ceiling height in m x 0.75 for hallways). Space 2.5-3m apart. For beds/artwork: Above seated shoulder; light width 1/2-2/3 artwork width. Extend ≤10cm from wall for safety.

Lighting Guide by Room Type

Use the above formulas, adjusted for room function. Below is a table with recommended sizes, fixture types, and tips (including hanging/spacing).


Room Type Recommended Fixture Size Fixture Types Hanging/Spacing Tips
Living Room Diameter: (L + W in m) x 10 cm. Height: Ceiling m x 20-25 cm. Chandeliers, pendants, flush mounts, floor/table lamps. Hang chandeliers/pendants ≥2.1m from floor. Use flush mounts for low ceilings (<2.4m). Layer with task lamps proportional to furniture (floor lamps 145-160cm tall).
Dining Room Diameter: 1/2-2/3 table width. For multiples: Each 1/3 table width. Chandeliers, linear pendants, sconces. Hang 80-90cm above table. Space multiples evenly for long tables.
Kitchen Each pendant: 1/4 island length. Pendants, recessed, under-cabinet, track lights. Hang pendants 80-90cm above counter. Space evenly; add under-cabinet for task lighting.
Bedroom Diameter: (L + W in m) x 10 cm. Flush/semi-flush mounts, bedside lamps, sconces, floor lamps. Bedside lamps at eye level when seated (total height ≈ nightstand height; shade height 1/2-2/3 lamp height, width 2x base). Flush mounts for ambient light.
Bathroom Diameter: (L + W in m) x 10 cm for ceiling lights. Vanity lights, sconces, flush mounts, recessed. Mount sconces 165-175cm from floor, 60cm above mirror for even task lighting.
Entryway/Hallway Diameter: (L + W in m) x 10 cm for entry. Even spacing in hallways. Chandeliers, flush mounts, sconces. Hang ≥2.1m from floor. Space hallway lights every 2.4-3m.
Home Office Diameter: (L + W in m) x 10 cm. Flush mounts, desk lamps, recessed, track lights. Desk lamps for focused task light (height 50-70cm, adjustable arm); recessed/track for larger spaces.

Ceiling Height Considerations

  • Low (<2.4m): Flush/semi-flush mounts to save space.
  • Standard (2.4-3m): Chandeliers/pendants; ensure ≥2.1m floor clearance.
  • High (>3m): Larger, dramatic fixtures to fill vertical space.

By following these guidelines, your fixtures will illuminate effectively and enhance any room's aesthetics.