Arc angle = central angle subtending the arc
If arc length and radius are known: angle in radians = arc length ÷ radius
If arc length and radius are known: angle in degrees = (arc length ÷ radius) × 180 ÷ π
If circumference and arc length are known: angle in degrees = (arc length ÷ circumference) × 360
If sector area and radius are known: angle in radians = 2 × sector area ÷ radius²
If sector area and radius are known: angle in degrees = (2 × sector area ÷ radius²) × 180 ÷ π
If the full circle angle is known, use proportionality: arc angle = 360 × (arc length ÷ circumference)
For a minor arc, use the smaller central angle
For a major arc, use 360° minus the minor arc angle