Instantly work out Beam Angle, Throw Distance and Spot Width for your lighting projects.
Have you ever found yourself needing to quickly work out how wide a beam of light will be at a certain distance, but didn’t have the formula to hand? Or perhaps you knew the spot size you wanted, but didn’t know which beam angle would achieve it.
That’s exactly why we’ve created our brand-new Lighting Beam Angle Calculator! Now available on our website, this free tool helps lighting professionals, hire production companies and installers instantly calculate beam angle, throw distance or spot width, saving you time and helping you plan your project more accurately.
Because the calculator works directly in your browser, it’s quick to use on desktop, tablet or mobile.
What is Beam Angle?
The beam angle of a lighting fixture describes how wide the light spreads as it leaves the lens. A narrow beam angle (for example 10°) produces a tight, focused spot of light, while a wide beam angle (for example 60°) products a much broader wash. Tighter beam angles tend to have a much denser, and brighter beam, whilst wider angles have a less intense, more washed-out beam, as the light is covering a larger area of space. This of course depends on the power engine and LED driving your lighting fixture.
Choosing the correct beam angle is critical for ensuring the right coverage, brightness and effect in your venue or live event.
Why does Beam Angle Matter?
Beam angle is direct related to the throw distance (the distance from the fixture to the surface) and spot width (the diameter of the light circle on that surface). Understand how these three values interact helps you:
- Select the right fixtures for your space
- Ensure consistent coverage across a stage or room
- Avoid wasted light and therefore unnecessary power consumption
- Design lighting plots that match both creative and technical requirements
- Improve your mirror ball effects: A lighting fixture with the right distance and beam angle will create much brighter and effective reflections
How the Beam Angle Calculator Works
Our beam angle calculator uses the industry-standard formulas that link throw distance, beam angle and spot width. There’s no secret, it’s just simple trigonometry!
- Spot width (D) = 2 × Throw distance (L) × tan(θ ÷ 2)
- Beam angle (θ) = 2 × arctan(D ÷ (2L))
- Throw distance (L) = D ÷ (2 × tan(θ ÷ 2))
Simply enter any two known values – for example, throw distance and beam angle – and the calculator will instantly work out the missing figure. You can switch between metres and feet depending on your preference, making it useful for both UK and international projects.
When to Use this Calculator
This tool is handy at several stages of a project:
- Design and specification – checking coverage when choosing the fixtures
- Quoting – you can provide accurate recommendations for your clients
- On-site – make quick calculations when adjusting rig positions. Things don’t always go to plan!
- Education and training – explain the relationship between beam angle, throw and spot size to your team, colleagues and clients
Final Thoughts
We created this tool to help save you time and make technical planning easier. Whether you’re designing a theatre rig, installing house lighting or preparing for a live production, this calculator can give you an accurate answer in seconds. We hope you find it useful!
