Geometry Calculators

Area, perimeter, volume and surface area of common shapes and solids.

All geometry calculators

• Area CalculatorChoose a shape, enter the measurements you know and get its area in the unit you prefer. Triangles can be solved from sides, angles, or a hypotenuse and a leg.
• Area of a Circle CalculatorEnter the radius and pick a unit to get the area of the circle in square units. The guide covers the formula, how to start from a diameter or circumference, and a quick lookup table.
• Area of a Parallelogram CalculatorEnter the base and the perpendicular height, pick a unit for each, and choose the unit for the answer. The guide shows the formula, the sine version and the usual pitfalls.
• Area of a Rectangle CalculatorEnter the width and length, choose a unit and read the area in square units straight away. Below you will find the formula, worked examples and the mistakes to avoid.
• Area of a Sector CalculatorGive the radius and the angle at the centre and the calculator returns the area of the slice in square units. The guide explains the formula and related quantities such as arc length.
• Area of a Square CalculatorType the side length of a square, pick a unit and press the button to get its area in square units. The guide below shows the formula, a few worked examples and how the diagonal or perimeter fits in.
• Area of a Trapezoid CalculatorEnter the two parallel sides and the perpendicular height of a trapezoid, choose a unit for each measurement and a unit for the result. The guide explains the formula, where it comes from and how to use it when a side is missing.
• Area of a Triangle CalculatorChoose what you know about the triangle, enter the measurements and get the area in the unit you prefer. The guide lists the formula behind each case and works through an example for every one of them.
• Area of Octagon CalculatorEnter the length of one side of a regular octagon and choose a unit to get its area in the matching square unit. The guide below shows the formula, where it comes from and how to use it.
• Circumference of a Circle CalculatorEnter the radius of a circle and pick a unit to get the distance around it. The guide below explains the formula, the role of pi and a few practical uses such as wheel travel.
• Cone Volume CalculatorEnter the radius of the cone's base and its height, choose the unit, and the calculator returns the volume in cubic units. The guide explains the formula and how to avoid the usual slips.
• Cylinder Volume CalculatorEnter the radius of the circular base and the height of the cylinder, pick a unit, and the calculator returns the volume in cubic units. The guide below explains the formula and shows how to work backwards.
• Endpoint CalculatorEnter the (x, y) coordinates of one end of a line segment and of its midpoint, and the calculator returns the coordinates of the other end. The guide explains the formula and checks it with examples.
• Hexagon CalculatorTell the calculator one measurement of a regular hexagon and it works out the rest: area, perimeter, both diagonals, the circumradius and the apothem. The guide gives every formula and four worked examples.
• Midpoint CalculatorType the (x, y) coordinates of the two end points and the calculator returns the point exactly halfway between them. The guide below explains the formula and where midpoints are used.
• Perimeter CalculatorPick a shape, enter its measurements in any mix of units and read the perimeter in the unit you choose. The guide lists the formula for each shape with a worked example.
• Perimeter of a Rectangle CalculatorEnter the width and the length of a rectangle, choose the unit, and the calculator gives the perimeter in that unit. Below you will find the formula, worked examples and a few related shortcuts.
• Perimeter of a Square CalculatorEnter the length of one side of a square, pick the unit, and the calculator returns the perimeter in that unit. The guide covers the formula and the shortcuts from area or diagonal.
• Perimeter of a Triangle CalculatorChoose which three measurements you know, enter them with their units, and the calculator works out the missing sides and returns the perimeter. The guide explains each rule with a checked example.
• Sphere CalculatorSay which measurement of the sphere you already know, type it in, and the calculator works out the rest: radius or diameter, surface area and volume. Choose the output unit and the answers arrive ready to use.
• Sphere Volume CalculatorEnter the radius of the sphere and choose its unit to get the volume in cubic units. Below you will find the formula, a worked example, a quick reference table and answers to common questions.
• Surface Area CalculatorChoose a shape, enter its measurements in any mix of units, and get the total outside area in the square unit you prefer. The guide lists the formula and a worked example for every shape.
• Volume CalculatorPick a solid, enter its dimensions in whichever units you measured them in, and get the volume in the cubic unit you prefer. Formulas and worked examples for each shape are below.
• Volume of a Box CalculatorEnter the length, width and height of a rectangular box, pick the unit, and the calculator returns the volume in the matching cubic unit. The guide covers the formula, unit conversions and shipping uses.
• Volume of a Cube CalculatorType the length of one edge, choose the unit, and get the cube's volume in the matching cubic unit. The guide shows the formula, worked examples and how to go backward from volume to side.
• Volume of a Prism CalculatorThis calculator finds the volume of a triangular prism from three measurements: the length of the prism and the base and height of its triangular end. The guide explains the formula and what each measurement means.