Area of some rectilinear figures
 Area of a Triangle : 1/2 x Base x Heights
 Area of Equilateral Triangle : Sqrt(3)/4 x (Side)^{2}
 Area of a Triangle – Hero’s formula :
 Sqrt{s (s – a) (s – b) (s – c)} where 2s = a + b + c.
 Area of Rectangle = Length x Breadth
 Area of a Square = (Side)^{2}
 Area of Four Walls = 2 x height (Length + breadth)
 Area of Rhombus = 1/2 x (Products of Diagonals)
 Area of Trapezium = 1/2 x (Sum of Parallel Sides) x (Distance between Parallel lines)
 Area of Parallelogram = Base x Altitude
 Somestandards units of Area
 100mm^{2} = 1 cm^{2}, 100 cm^{2}, = 1 dm^{2}
 100dm^{2} = 1 m^{2}, 100 m^{2}, = 1 are
 100arcs = 1 hactare
 100 hactare = 1 km^{2}
Area related to Circles:
Circumference of a Circle or 

Circumference (Perimeter) 

Circle: 

Area of a Circle = r^{2} 

Area of a SemiCircle = r^{2}  
Area of a Quadrant = r^{2}  
Perimeter of a Semi 

Perimeter of a Semi Circle : r + 2r 

Area of a Ring: 

Area of a ring or Annulus : (R^{2} – r^{2}) 

Length of arc: 

Length of arc AB = or  
Area and Perimeter of a Sector : 

Area of a Sector OACBO = or (l x r)  
Area of a Sector OACBO = Length of arc AB + 2r  
Area of a Segment : 

Area of a Minor Segemnt ACBA : Area of a sector OACBO – Area of Triangle OAB = – r^{2}sin(theta) 

Area of a Major Segment BDAB : Area of a circle – Area of a minor segment ACBA =r^{2} – Area of minor segment ACBA 
Surface Area and Volumes:
Cuboid: If the length of a cuboid is l, breadth is b (sometimes we also use breadth as width ‘w’) and the height is ‘h’. The formula for the lateral surface area, total surface area and its volume of a cuboid are 

Lateral Surface area of a Cuboid= Area of four walls = 2 (length + breadth) x height = 

Total Surface area of a Cuboid = 2 (length x breadth + breadth x height + height x length) 

Volume of a Cuboid = length x breadth x height = lbh 

Cube : Basically a cube is a special type of a cuboid in which length, breadth and its height are equal i.e. length = breadth = height and it is also called an edge of a cube. The formula for the lateral surface area, total surface area and its volume of a cube are 

Lateral Surface area of a Cube = Area of four walls = 4 (edge)^{2} 

Total Surface area of a Cube = 6 x (edge)^{2} 

Volume of a Cuboid = (edge)^{3} 

Right Circular Cylinder : It the radius of a right circular cylinder is ‘r’ and its height is ‘h’. Then the curved surface area, total surface area and volume formula is given by 

Area of the base of a cylinder = r^{2} 

Area of curved surface = Lateral surface area = Perimeter of the base x Height of cylinder 

Total surface Area = 2rh + 2r^{2 } = 2r (h + r) 

Right Circular Hollow Cylinder : If the radius of internal and external cylinder is ‘r’ and ‘R’ respectively. Then the formula for curved and total surface area, volume of a hollow cylinder is given by 

Area of curved surface = (Area of External Surface) + (Area of Internal Surface) 

Total Surface Area = Curved surface area + 2 (Area of the base ring) 

Volume of a hollow cylinder : Exterior Volume – Internal Volume 

Right Circular Cone: If r be the radius, h be the height and l be the slant height of a right circular cone. Then the slant height, area of its curved surface and volume is given by the formula 

Slant height (l) = √(h^{2} + r^{2}) 

Area of a Curved Surface = rl = r √(h^{2} + r^{2}) 

Total Surface area = Area of a curved surface + Area of a Base 

Volume of a cone = 1/3 r^{2}h 

Sphere: If r be the radius of a sphere. Then the formula for its surface area and its volume is given by 

Surface Area = 4r^{2} 

Volume = 4/3 r^{2} 

Spherical shell : If r be the radius of internal, and R be the radius of external spherical shell. Then the surface area and volume is given by the formula 

Curved Surface Area = 4R^{2} 

Volume = 4/3 R^{3} – 4 /3 r^{3}= 4/3 (R^{3} – r^{3}) 

Hemisphere: If r be the radius of internal, and R be the radius of external spherical shell. Then the surface area and volume is given by the formula 

Curved Surface Area = 2r^{2} 

Total Curved Surface Area = Area of curved Surface + Area of its Base = 2r^{2} + r^{2} = 3r^{2} 

Volume = 2/3 r^{3} 

Frustum of a Cone : Fructum is a latin word and the meaning is ‘piece cut off’. If any right circular cone is cut off by a plane, which is parallel to its base, then the portion of the cone between the plane and the base of a cone is known as a fractum of a cone. Then the formula for curved and total surface area, volume of a frustum of a cone is given by 

Curved Surface Area = l (R + r) where l = √[h^{2} + (R – r) ^{2}] 

Total Curved Surface Area = [R^{2} + r^{2} + l (R + r)] 

Volume = 1/3 h [R^{2} + r^{2} + Rr] 

Here : h = Vertical height of the frustum l = slant height of the frustum R = radius of the top r = radius of the bottom 