Projector Calculator — Screen Size from Throw Distance
Enter the distance from your projector to the screen and its throw ratio to instantly calculate the screen width, height, and diagonal in both metres and inches.
m
Aspect ratio
2.29 m — at 3.0 m throw with 1.5 throw ratio
- 1
Screen width
3 m ÷ 1.5 = 2 m - 2
Screen height
2 m × (9 ÷ 16) = 1.125 m - 3
Diagonal (m)
√(2² + 1.125²) = 2.295 mPythagoras: diagonal² = width² + height². - 4
Diagonal (inches)
2.295 ÷ 0.0254 = 90.3
How does this calculator work?
Screen width = throw distance ÷ throw ratio. Height = width × (aspect-ratio fraction). Diagonal = √(width² + height²). Enter your room depth and projector throw ratio to find the maximum screen size — check your projector spec sheet for its specific throw ratio (typically 0.4–2.5).
Formula
How this is calculated
The throw ratio is the key spec on every projector: it equals throw distance divided by image width. So if you know your room depth (throw distance) and your projector's throw ratio, dividing them gives the maximum image width. Multiply by the aspect-ratio fraction to get height, then use Pythagoras to find the diagonal.
Typical throw ratios are 1.3–2.0 for standard throw projectors, 0.4–0.8 for short throw, and below 0.4 for ultra-short throw. Check your projector's manual or specification sheet for the exact value — many projectors also have a zoom range, giving a range of throw ratios rather than a single number. Use the minimum ratio for the largest possible image and the maximum ratio for the smallest.
All outputs are in both metres and inches so you can match standard screen sizes advertised in inches. Note that screen dimensions assume the projector fills the full screen and is correctly aligned — keystone correction or offset lenses may shift the image position but do not change the calculated size.
Frequently asked questions
It is listed in the projector's specification sheet, usually labelled "throw ratio" or "projection ratio." For zoom lenses you will see a range such as 1.5–2.0; use the smaller end for the largest image at a given distance.
Yes — enter distance in feet and the width and height results will also be in feet. The diagonal in inches is calculated from the metric conversion and will still be correct regardless of the unit you enter, as long as you use the same unit for distance throughout.
No — it calculates physical screen dimensions only. Screen gain, projector lumens, ambient light, and room colour affect image brightness but not the size calculation.
Also known as
TG we-Calculate Editorial Team. (2026). Projector Calculator — Screen Size from Throw Distance [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/projector-calculator
TG we-Calculate Editorial Team. "Projector Calculator — Screen Size from Throw Distance." TG we-Calculate. 2026. https://we-calculate.com/calculator/projector-calculator.
TG we-Calculate Editorial Team, "Projector Calculator — Screen Size from Throw Distance," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/projector-calculator
@misc{wecalculate_projector_calculator, title = {Projector Calculator — Screen Size from Throw Distance}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/projector-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?