Simplified maths for metalwork

• Area of a circle = πr² ≈ 3.1416 × radius × radius
• Circumference of a circle = πd ≈ 3.1416 × diameter
• Diameter of a circle = c ÷ π ≈ circumference ÷ 3.1416
• Area of an oval = πab (where a is ½ longest diameter and b is ½ shortest diameter)
  ≈ longest diameter × shortest diameter × 0.7854
• Circumference of an oval = 2 × pi × sqrt(a^2 + b^2) ÷ 2) (where a is the longest diameter and b is the shortest diameter)
  ≈ (a + b) × 1.5708
• Area of a triangle = ½ × width × height
• A circle is 0.7854 (π ÷ 4) times the area of a square of the same dimensions.