Zenova – Japanese Wood Floor Lamp

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).

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.