# Screen angle calculation

**URL:** <https://mworks.discourse.group/t/screen-angle-calculation/249>\
**Category:** Support\
**Created:** [May 31, 2019, 1:47pm UTC](https://mworks.discourse.group/t/screen-angle-calculation/249 "2019-05-31T13:47:52Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\
**Post date:** [May 31, 2019, 1:47pm UTC](https://mworks.discourse.group/t/screen-angle-calculation/249/1 "2019-05-31T13:47:52Z")

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Hi Chris,

Last week I was setting up mWorks in a new setup and to verify I had gotten all the screen size and distance measurements correctly, I measured the size of a 10 degree stimulus on the screen and after doing some trigonometry, I discovered it was actually being displayed at an 11 degree size. I double checked all my measurements and my math and I am fairly sure they are correct. I was wondering if you might be able to tell me what assumptions/equations mWorks makes when computing the size to display a stimulus (for example, does it assume a spherical screen?) or if you have any other thoughts on what else could cause this oddity.

Thanks,

Simon

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**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\
**Post date:** [May 31, 2019, 1:59pm UTC](https://mworks.discourse.group/t/screen-angle-calculation/249/2 "2019-05-31T13:59:53Z")

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Hi Simon,

There’s a pretty detailed description of how MWorks computes the bounds of the screen in degrees of visual angle in [another discussion](https://mworks.tenderapp.com/discussions/problems/113#comment_33631307). It doesn’t make any assumptions about the shape of the screen, but it does assume there’s enough distance between the screen and the subject for the [small angle approximation](https://en.wikipedia.org/wiki/Small-angle_approximation) to be valid.

Cheers,  
Chris

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**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\
**Post date:** [July 19, 2022, 8:50pm UTC](https://mworks.discourse.group/t/screen-angle-calculation/249/3 "2022-07-19T20:50:06Z")

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