Beam spread, or beam angle, measures the spread of light (the width of the beam) from a reflectorized light source. The beam spread number is important to know when deciding how much light you want displayed on an object, a sign, or on your floors. Knowing the beam spread number also helps you purchase the right light bulbs for the desired lighting effect you want.

Measure Beam Spread

Spot Beam vs. Flood

Reflector lamps have either a spot or flood beam depending on their size. The difference between a spot beam and a flood is the width of the beam, or the beam spread. Having both styles gives you more lighting options throughout your property.

Spot Beams:

  • Output a narrow beam of light, usually less than 45 degrees
  • Most of the light is concentrated into a smaller area
  • Ideal for track lighting, nighttime walkways, displays, and recessed trims

Flood Beams:

  • Output a much wider beam of light, typically up to 120 degrees
  • Provides a fuller light stream to illuminate larger areas
  • Great for landscaping, ceiling lights, security, and signage

How to Measure Beam Spread

To find the beam width from a given distance, use this simple formula:

Angle of Beam x .018 x Distance = Beam Spread

Let's say you need to know the beam spread of a 120 degree floodlight from a distance of 15 feet. Just plug in the numbers into the formula shown above:

120 x .018 x 15 = 32.4

Beam Spread Chart

To make calculations easy, use this handy table to determine beam spread.

Beam Spread Chart