Angular Size Calculator
Enter how big an object is and how far away it is, in any units. The calculator works out how big it looks, as an angle in degrees, arcminutes, arcseconds and radians.
- Any size and distance
- Degrees to arcseconds
- Moon comparison
Size is measured across the object at right angles to your line of sight.
Angular size is how large something looks, not how large it is. A coin at arm's length and the Moon in the sky look about the same size because they cover the same angle. Astronomers, photographers and sign designers all use angular size to know what the eye or a camera will actually see.
Angular size chart
Familiar things. Search for an object.
| Object | Angular size | Arcminutes |
|---|---|---|
| Sun | 0.53° | 32 |
| Full Moon | 0.52° | 31 |
| Jupiter at its largest | 0.013° | 0.8 |
| Thumb at arm's length | 2° | 120 |
| Fist at arm's length | 10° | 600 |
| Coin (24 mm) at 2.6 m | 0.53° | 32 |
| Person (1.75 m) at 100 m | 1° | 60 |
| Human eye resolution | 0.017° | 1 |
Your hand at arm's length makes a handy angle gauge. Little finger about 1°, three fingers about 5°, a fist about 10°.
Distance and apparent size
A 1.75 m person. Slide the distance.
At 200 m a person covers about half a degree, the same as the full Moon.
How to work out angular size
One formula. Step through it.
Same units
Convert size and distance.
For small angles, size ÷ distance in radians is close enough. For close objects use the full formula.
Degrees, arcminutes or arcseconds
Units of angle. Compare them.
360 in a circle. Good for everyday angles.
A sixtieth of a degree.
A sixtieth of an arcminute.
Telescope and lens specifications often quote resolution in arcseconds. The human eye resolves about one arcminute.
Using angular size
Practical checks. Tick each item.
Tick each item as you go.
For signs, text must cover at least about 0.3° to be read comfortably. That means 5 mm letters at about 1 m.
What you get
Angle in every unit. Each tile explains one result.
In degrees.
Degrees, minutes, seconds.
For maths.
For astronomy.
Compared with the full Moon.
The Moon comparison is a quick way to picture any small angle in the sky.
Frequently Asked Questions
No question matches that search.
What is angular size?
The angle an object covers as seen from where you are.
How do I calculate angular size?
θ = 2 × arctan(size ÷ (2 × distance)).
What is the angular size of the Moon?
About 0.52°, or 31 arcminutes.
Why do the Sun and Moon look the same size?
The Sun is about 400 times wider but also about 400 times further away.
What is an arcminute?
One sixtieth of a degree.
How small can the human eye see?
About one arcminute, under good conditions.
Does angular size change with distance?
Yes. Double the distance and the angle roughly halves.
See how big things look
Enter a size and a distance, and get the angle in the unit you need. It works for planets, signs, photos and anything else you want to picture.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.