Categories October Surprise 2024 5 Ways to Calculate the Area of a Circle – wikiHow Post author By Post date September 22, 2026 To find the area of a circle, use the formula A = Ļ ā¢ r2, where r is the radius of the circle. If you only know the diameter of the circle, then use the formula A = Ļ ā¢ (d/2)2 where d is diameter.