Geometry Calculators
Pick a shape, enter what you know, and solve for everything else. Plane figures from circles to regular polygons, solids from cubes to frustums — with the formulas laid out.
47 calculators
Most used
- Circle CalculatorKnow one measurement of a circle — radius, diameter, circumference or area — and get the other three instantly.
- Pythagorean Theorem CalculatorEnter two sides of a right triangle to find the third with a² + b² = c², including exact radical answers, both acute angles and the area.
- Triangle CalculatorEnter three measurements that fix a triangle and get the missing sides and angles, area, perimeter, heights, medians and circle radii.
- Volume CalculatorPick a 3D shape, enter its dimensions and get the volume in cubic units plus the capacity in liters and US gallons.
Plane geometry (2D) 14
- 2D Shape FormulasA working formula sheet for flat shapes. Pick one, enter its dimensions and see every area and perimeter formula with your numbers plugged in.
- Annulus CalculatorFind the area, width and edge lengths of a ring between two concentric circles, or the hole size that gives a target area.
- Circle CalculatorKnow one measurement of a circle — radius, diameter, circumference or area — and get the other three instantly.
- Circle Sector & Arc Length CalculatorSolve a pie-slice sector of a circle for its area, arc length, chord, segment and central angle from two known measurements.
- Ellipse CalculatorFind the area, perimeter, focal distance and eccentricity of an ellipse from its axes, its eccentricity or its area.
- Hexagon CalculatorEnter any one measurement of a regular hexagon — side, across flats, across corners, apothem, perimeter or area — and get all the others.
- Octagon CalculatorFind every measurement of a regular octagon from one known value, including all three diagonal lengths and the corner cut for a square.
- Parallelogram CalculatorSolve a parallelogram from two sides and an angle, height or diagonal, and see why its area is base times height rather than side times side.
- Rectangle CalculatorEnter two facts about a rectangle (sides, diagonal, area or perimeter) and get the rest, including the diagonal and aspect ratio.
- Regular Polygon CalculatorEnter the number of sides and one measurement to get the side, area, perimeter, apothem, circumradius and angles of a regular polygon.
- Rhombus CalculatorWork out every measurement of a rhombus, the four-equal-sided diamond, from its two diagonals or from a side plus one more value.
- Square CalculatorTurn a single square measurement into the side, diagonal, perimeter and area, plus the radii of the circles inside and around it.
- Stadium CalculatorWork out the area, perimeter and dimensions of a stadium shape, a rectangle capped by two half-circles, from whatever you can measure.
- Trapezoid CalculatorGet the area, height, perimeter, angles and diagonals of any trapezoid from its two bases and the height, the legs or the area.
Triangles 9
- Equilateral Triangle CalculatorEnter any one measurement of an equilateral triangle and get its side, height, area, perimeter, inradius and circumradius.
- Isosceles Triangle CalculatorGive two measurements of an isosceles triangle, such as the legs, base, height or an angle, and get every other side, angle and the area.
- Law of Cosines CalculatorFind a triangle's missing side from two sides and an angle, or its three angles from three sides, with the full law of cosines working.
- Law of Sines CalculatorSolve a triangle from two angles and a side, or from two sides and a non-included angle, including both answers in the ambiguous case.
- Pythagorean Theorem CalculatorEnter two sides of a right triangle to find the third with a² + b² = c², including exact radical answers, both acute angles and the area.
- Right Triangle CalculatorEnter two known values of a right triangle, such as two sides or a side and an angle, to get every side, both acute angles and the area.
- Triangle Area CalculatorWork out a triangle's area four ways, from base and height, three sides, two sides and the included angle, or the coordinates of its corners.
- Triangle CalculatorEnter three measurements that fix a triangle and get the missing sides and angles, area, perimeter, heights, medians and circle radii.
- Circumcircle & Incircle CalculatorFind the circumscribed and inscribed circles of a triangle from three sides or three vertices, with radii, centers, areas and a diagram.
Solid geometry (3D) 18
- 3D Shape FormulasA formula sheet for solid shapes. Pick one, enter its dimensions and see every volume and surface formula worked out with your numbers.
- Capsule CalculatorGet the volume, capacity and surface area of a cylinder with hemispherical ends from its radius plus the straight length, overall length or volume.
- Cone CalculatorFind a cone's volume, slant height, surface areas and angles from any two measurements, or the size that holds a set volume.
- Conical Frustum CalculatorEnter both radii of a cut-off cone plus its height, slant height or volume to get its capacity, surface areas and the height of the original cone.
- Cube CalculatorKnow one measurement of a cube and get its edge, volume, surface area, both diagonals and capacity in liters and gallons.
- Cylinder CalculatorWork out the volume, capacity and surface area of a cylinder, or find the height or radius that gives the volume you need.
- Ellipsoid CalculatorCalculate the volume and the exact surface area of any ellipsoid, including oblate and prolate spheroids, from its three axes.
- Hemisphere CalculatorFind the volume, capacity, curved dome area and total surface area of half a sphere from any one measurement.
- Pyramid Frustum CalculatorFind the volume and surface area of a truncated pyramid with a square, triangular, hexagonal or other regular base from its top and bottom edges.
- Rectangular Prism CalculatorWork out the volume, surface area and diagonals of any box, room or tank, or find its height from a target volume, diagonal or surface area.
- Sphere CalculatorEnter one measurement of a ball or spherical tank and get its radius, diameter, surface area, volume and capacity.
- Spherical Cap CalculatorCalculate the volume, dome surface area, base radius and height of a spherical cap from any two of sphere radius, base radius and height.
- Square Pyramid CalculatorFind a square pyramid's volume, surface area, slant height and lateral edge from whichever two measurements you have.
- Surface Area CalculatorChoose a 3D shape and get its total surface area, broken down into sides and bases, plus the volume for reference.
- Torus CalculatorCalculate the volume, surface area and dimensions of a torus from its major and minor radii or its inner and outer radii.
- Triangular Prism CalculatorGet the volume, total surface area and every face of a triangular prism from the triangle at its end and its length.
- Tube CalculatorWork out how much material is in a pipe or tube, how much it holds, its inner and outer surface areas and an estimated weight.
- Volume CalculatorPick a 3D shape, enter its dimensions and get the volume in cubic units plus the capacity in liters and US gallons.
Coordinate geometry 6
- 3D Distance CalculatorFind the distance between two points in space from their x, y and z coordinates, plus the midpoint and the angle the segment makes with each axis.
- Circle Equation CalculatorFind a circle's standard and general equations from its center and radius, a diameter, three points, or the general form, with a graph.
- Distance CalculatorEnter the coordinates of two points to get the straight-line distance between them, its exact square-root form and the grid (Manhattan) distance.
- Midpoint CalculatorAverage two endpoints to find the midpoint of a segment, or recover a missing endpoint from the midpoint, in two or three dimensions.
- Polygon Area CalculatorEnter a polygon's corner coordinates in order to get its area by the shoelace formula, plus perimeter, centroid, orientation and convexity.
- Slope CalculatorGet a line's slope as a fraction, decimal, percent grade and angle from two points, plus its intercepts and its equation in three common forms.
Guides
- How to Calculate Volume: Formulas for Boxes, Cylinders, Cones and SpheresMost volume formulas are base area times height, with a factor of one-third for pointed shapes. Formulas, worked examples and unit conversions.
- How to Find the Area of a Circle (From Radius, Diameter or Circumference)Area equals pi times the radius squared. Learn the formula, the diameter and circumference versions, real-world examples and partial circles.
- How to Find the Area of a Triangle: 5 Formulas and When to Use EachPick the triangle area formula that matches what you know: base and height, three sides, two sides and an angle, or corner coordinates.
- How to Find the Slope of a Line (From Two Points or an Equation)Slope is rise over run. Find it from two points, a graph or an equation, and convert it to a percent grade or angle for ramps, roofs and roads.
- How to Use the Pythagorean Theorem (a² + b² = c²)Find any missing side of a right triangle with a² + b² = c². Worked examples for ladders, screens, square corners and 3D diagonals.