﻿ Useful Conversion Formulae  • Circumference of a circle = diameter x 22/7 (or 3.1416)
• Area of a circle = square of the diameter x 0.7854
• Area of a square, rhombus or rhomboid = base x height
• Area of a triangle = 1/2 base x perpendicular height
• Area of a trapezium = 1/2 sum of two parellel sides x height
• Area of any rectilinear figure of four or more unequal sides is found by dividing it into triangles, finding the area of each, and adding together
• Area of any regular polygon = 1/2 radius of inscribed circle x length of sides x number of sides
• Area of a parabola = base x height x 2/5
• Area of an elipse = long axis x short axis x 0.7854
• Surface of a prism or cylinder = area of two ends + (length x perimeter); volume = area of base x height
• Surface of a cone or pyramid = 1/2 (slant height x perimeter of base) + area of base; volume = 1/3 (area of base x perpendicular height)
• Surface of a cube or parallelepiped = sum of areas of all sides; volumes = length x breadth x depth
• Surface of a sphere = square of diameter x 3.1416; volume = cube of diameter x 0.5236
• Area of a sector of a circle = length of arc x 1/2 radius
• Area of a segment of a circle = area of a sector less area of a triangle
• Side of a square of area equal to a circle = diameter x 0.8862
• Diameter of a circle equal in area to a square = side x 1.1284
• Area of a regular hexagon = 0.8661 x (width across flats)²; width of flats
• Area of a regular octagon = 0.8284 x (width across flats)²; width of flat = 0.4142 x width across flats