Angular Size Calculator
Angular size is how wide something appears from where you stand, not its true width, which is why the Moon and the Sun look almost the same size despite the Sun being vastly larger and farther away. The small angle formula relates the true diameter, the distance and the apparent angle: the angle in radians is the diameter divided by the distance. This calculator converts that into degrees, arcminutes and arcseconds using the same units for size and distance, so you can compare planets, craters or a distant building. You can also enter the angle and distance to recover the true size. All arithmetic happens instantly in your browser with nothing sent anywhere.
How to use Angular Size Calculator
- Enter the true diameter and the distance in matching units.
- Or enter angular size and distance to solve for diameter.
- Read the apparent size in degrees, arcminutes and arcseconds.
Frequently asked questions
How does this find apparent size in the sky?
It applies the small angle formula, so apparent size is the true diameter divided by distance, then converts that angle to degrees, arcminutes and arcseconds.
Can it work backwards to a real diameter?
Yes; give it the angular size and the distance and it solves for the true diameter of the object using the same relationship.
Why report three angle units at once?
The Moon spans about half a degree, planets a few tens of arcseconds and faint targets less, so degrees, arcminutes and arcseconds each suit a different scale.
What is Angular Size Calculator?
Angular size is how wide something appears from where you stand, not its true width, which is why the Moon and the Sun look almost the same size despite the Sun being vastly larger and farther away. The small angle formula relates the true diameter, the distance and the apparent angle: the angle in radians is the diameter divided by the distance.
Is Angular Size Calculator free to use?
Yes. Angular Size Calculator is completely free, with no sign-up and no usage limits.
Does Angular Size Calculator work in a web browser?
Yes. Angular Size Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with Angular Size Calculator?
Yes. Angular Size Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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