Geometry calculators
57 calculators
Geometry calculators find area, perimeter, volume, and related measures for plane and solid figures. This hub groups 2D shapes, triangles, circles, angles, and 3D solids so you can open the page that matches the figure you actually have.
Formulas assume the dimensions labeled on the page (radius, side length, and so on). Selected tools include diagrams; every tool shows the identity in How it works. Shape calculators are free to use with no sign-up.
2D geometry calculators
Area, perimeter, and plane figures: polygons, ellipses, and related measures.
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Area
Rectangle area from length and width.
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Chord Length Calculator
Chord length from radius and central angle in degrees.
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Ellipse Area Calculator
Area of an ellipse from semi-axes a and b.
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Golden Rectangle Calculator
Longer side and area of a golden rectangle from the shorter side.
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Kite Area Calculator
Area of a kite from diagonals.
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Parallelogram Area Calculator
Area of a parallelogram from base and height.
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Perimeter Calculator
Perimeter of a rectangle, or of n equal sides (regular polygon) via mode.
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Polygon Angles Calculator
Interior sum and each exterior angle for a regular polygon.
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Quadrilateral Area Calculator
Area of a simple quadrilateral from four vertices (shoelace).
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Regular Polygon Area Calculator
Area of a regular polygon from sides and side length.
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Rhombus Area Calculator
Area of a rhombus from diagonals p and q.
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Segment Area Calculator
Area of a circular segment from radius and central angle in degrees.
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Trapezoid Calculator
Area of a trapezoid from two parallel sides and height.
Triangle calculators
Right, special, and general triangles: area, angles, similarity, and inequalities.
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30 60 90 Triangle Calculator
Sides of a 30-60-90 triangle from the short leg (opposite 30°).
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45 45 90 Triangle Calculator
Hypotenuse of an isosceles right triangle from a leg.
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Centroid of a Triangle Calculator
Centroid of a triangle from three vertex coordinates; reports G as the average of the vertices.
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Classifying Triangles Calculator
Name a triangle from three side lengths (equilateral, isosceles, scalene; acute/right/obtuse).
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Equilateral Triangle Calculator
Area, height, and perimeter of an equilateral triangle from side s.
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Heron's Formula Calculator
Triangle area from three side lengths.
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Isosceles Triangle Calculator
Area and vertex angle of an isosceles triangle from equal sides a and base b.
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Perimeter of a Triangle Calculator
Perimeter of a triangle from three sides.
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Pythagorean Triples Calculator
Check whether (a, b, c) is a Pythagorean triple (order-insensitive).
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Pythogorean Theorem
Hypotenuse of a right triangle from legs a and b (workbook spelling).
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Similar Triangles Calculator
Missing corresponding side given three known corresponding lengths (scale factor).
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Triangle Angle Calculator
Third angle of a triangle from two angles in degrees.
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Triangle Area Calculator
Area from base and height, or from three sides (set height to 0 to use Heron).
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Triangle Height Calculator
Height to side a from area, or from two sides and the included angle (SAS).
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Triangle Inequality Theorem Calculator
Test whether three lengths can form a triangle.
Circle calculators
Radius, circumference, arcs, sectors, and circle equations.
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Arc Length Calculator
Arc length from radius and central angle in degrees.
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Area of a Circle Calculator
Area of a circle from radius, diameter, or area; also diameter and circumference.
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Equation of a Circle Calculator
Radius and standard-form equation from center (h, k) and a point (x, y) on the circle.
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Sector Area Calculator
Area of a circular sector from radius and central angle in degrees.
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Semicircle Area Calculator
Area and curved-plus-diameter perimeter of a semicircle from radius.
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Tangent of a Circle Calculator
Tangent length from an external point to a circle of radius r about the origin.
Angle calculators
Complementary, supplementary, clock, central, and vector angles.
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Angle Between Two Vectors Calculator
Angle between two 2D vectors, in degrees.
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Central Angle Calculator
Central angle from arc length and radius (degrees).
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Clock Angle Calculator
Smaller angle between hour and minute hands.
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Complementary Angles Calculator
Complement of an angle in degrees (90° − θ).
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Coterminal Angle Calculator
Coterminal angle in [0, 360) degrees.
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Reference Angle Calculator
Acute reference angle for a degree measure.
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Supplementary Angles Calculator
Supplement of an angle in degrees (180° − θ).
3D geometry calculators
Volume and surface of solids: boxes, spheres, cylinders, cones, and more.
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Cone Calculator
Cone surface and volume.
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Cube Calculator
Volume, surface, face diagonal, and space diagonal of a cube.
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Cylinder Calculator
Cylinder surface and volume.
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Ellipsoid Volume Calculator
Volume of an ellipsoid from semi-axes a, b, c.
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Euler’s Formula for Polyhedra Calculator
Missing V, E, or F from Euler’s formula V − E + F = 2 (enter 0 for the unknown).
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Hemisphere Calculator
Volume and total surface (curved + base) of a hemisphere from radius.
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Pyramid Volume Calculator
Volume of a pyramid from base area and height.
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Slant Height Calculator
Slant height of a right circular cone from radius and vertical height.
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Sphere Calculator
Sphere surface area and volume from radius.
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Surface
Surface area of a rectangular box.
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Surface Area to Volume Ratio Calculator
S/V for a sphere, cube, or rectangular box; reports surface, volume, and the inverse-length ratio.
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Tetrahedron Volume Calculator
Volume of a regular tetrahedron from side a.
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Torus Calculator
Volume and surface of a torus from tube radius r and distance R to tube center.
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Triangular Prism Calculator
Volume of a right triangular prism from triangle sides a,b,c and length ℓ.
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Volume
Volume of a rectangular box.
Coordinate geometry calculators
Distance and other coordinate measures kept with geometry tools.