Image Size, Throw Distance & Beam Angle Calculator


Ever needed to project a gobo or image to be a specific size but don't know what beam angle you need? Want to know how big the pool of light will be from your lantern? Want to calculate how far away you need to place a lantern?

Now you can! Using a little java script and simple trigonometry, fill in what you know and click the button to calculate the missing number

Throw Distance Units
Beam Angle Degrees
Image / Beam Size Units

Notes: The angle must be in degrees. Distance & size can be either feet or metres - The answer will be in the same unit of measurement as your entry. You can't mix units. Don't try a 3ft image size with a 5m throw distance - The answer will be wrong!!!

This little calculator will work for all lantern manufactures, whether it be Selecon Pacific, an ETC Source 4 Profile, an Robert Juliat Followspot, Robe Moving Light - its only trigonometry.

1 metre = 3.2808399 feet

Meters Feet