Angular Size Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the object's size and its distance (same unit).
- Read the angular size.
How it works
Angular size = 2 × arctan(size ÷ (2 × distance)).
Worked example
Moon: 3474 km at 384,400 km. ≈ 0.52°.
Common mistakes
- Using different units for size and distance.
- Forgetting it's the full diameter, not the radius.
Frequently asked questions
Why do the Sun and Moon look the same size?
Coincidence of geometry — both span about half a degree, which is why total solar eclipses work.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.