1. What is a Downlight Beam Angle Calculator?

Definition: This calculator determines the beam angle of a downlight based on the diameter of the light beam at a specific distance from the light source.

Purpose: It helps lighting designers, architects, and homeowners calculate the spread of light from downlights for proper illumination planning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Beam Angle — The angle of light spread (degrees)
• Beam Diameter — Width of the light circle at the measured distance (feet)
• Distance — Measurement distance from light source (feet)

Explanation: The formula calculates the angle by determining the inverse tangent of the ratio between half the beam diameter and the distance, then doubling it.

3. Importance of Beam Angle Calculation

Details: Proper beam angle calculation ensures appropriate light distribution, avoids dark spots or over-illumination, and helps achieve desired lighting effects.

4. Using the Calculator

Tips: Measure the diameter of the light circle at a known distance from the light source. Enter both values in feet. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical beam angle for downlights?
A: Residential downlights typically have 25°-40° beam angles, while accent lighting might use 15°-25°.

Q2: How does beam angle affect lighting?
A: Narrower angles create focused light pools, wider angles provide more general illumination.

Q3: Should I measure at the working plane height?
A: Yes, measure at the height where the light will be used (e.g., 30" for countertops, 36" for tables).

Q4: Does this work for all light types?
A: This works best for directional lights like downlights and spotlights, not omnidirectional bulbs.

Q5: How accurate is this calculation?
A: It provides theoretical angle; actual light spread may vary based on reflector design and bulb type.