Visual Angle Calculator

Visual Angle

The visual angle of an object is a measure of the size of the object's image on the retina. The visual angle depends on the distance between the object and the observer -- larger distances lead to smaller visual angles. The visual angle also depends on the object's size -- larger objects lead to larger visual angles. Calculated size and distance are in the same unit of measurement as the input. E.g. if you enter the size in cm, the calculated distance will be in centimeters.

The visual angle is the angle formed from two imaginary lines projecting from the eye. One goes to the top (or left) of the object and the other goes to the bottom (or right) of the object. Visual angle is usually reported in degrees, minutes and seconds of the subtended angle. One minute of arc is 1/60^th of one degree of arc. One second of arc is 1/60^th of one minute of arc. Degrees (°), minutes (') and seconds ('') of arc describe the angle and therefore the size of the object's image on the retina.

The Calculator

Enter two of the following three items. Size and distance must be entered in the same units. Visual angle, if entered, must be in degrees (fractional degrees are fine; you may use neither minutes and seconds of subtended angle nor radians). If all three values are entered, the visual angle will be calculated from the size and distance values.

See also the visual angle demonstration.