Geometry calculators
Area, perimeter, volume and surface area for plane shapes and solids, triangle solving for every SSS–SSA case, circles, trigonometry and coordinate geometry, each with a drawing to scale.
12 calculators · 103 checked examples
Shapes
- Area and perimeter calculator for 2D shapes
Area and perimeter of 15 plane shapes, from rectangles, triangles and trapezoids to circles, ellipses, regular polygons and rings, drawn to scale.
- Circle calculator: area, circumference and radius
Area, circumference, radius and diameter of a circle from any one of them, plus arc length, chord, sector and segment area for a central angle.
Solids
Triangles
- Right triangle calculator: hypotenuse, sides and angles
Hypotenuse, missing leg, both acute angles, area and perimeter of a right triangle from any two values, using Pythagoras' theorem and SOHCAHTOA.
- Triangle calculator: solve SSS, SAS, ASA, AAS and SSA
Missing sides, angles, area, perimeter, heights, inradius and circumradius of any triangle from three measurements, with both SSA answers.
Trigonometry
Coordinates
- Slope, distance and midpoint calculator: line through two points
Distance, midpoint and slope between two points, the line's equation in slope-intercept, standard and point-slope form, and where two lines meet.
- Circle through three points: centre, radius and equation
Centre, radius and equation of the circle through three points, in standard form (x − h)² + (y − k)² = r² and general form, plus area.
- Polygon area from coordinates: shoelace formula calculator
Area, perimeter and centroid of any simple polygon from its vertex coordinates, using the shoelace (surveyor's) formula with every term shown.
Angles
- Angle converter: degrees, radians, DMS and gradians
Convert angles between decimal degrees, degrees-minutes-seconds (DMS), radians, gradians, turns, arcminutes, arcseconds and milliradians.
- Polygon angle calculator: interior and exterior angles
Sum of interior angles, each interior and exterior angle of a regular polygon and the number of diagonals, from the number of sides or one angle.
- Roof pitch and slope calculator: angle, grade and rise over run
Angle, percent grade and roof pitch (x in 12) from rise and run or from any one of them, with the sloped length and rafter factor.
Choosing a calculator: Geometry
Do I need area or volume?
Area covers a flat face in square units, so use it for a floor; volume fills a solid in cubic units, so use it for a container's capacity. Perimeter measures the boundary in units of length, and surface area counts the faces you would cover or paint.
Which calculator do I use for a circle?
The circle calculator works from either the radius or the diameter. Check which one you measured, because confusing them changes the area by a factor of four.
Which triangle calculator should I use?
Use the right-triangle calculator when one angle is exactly 90 degrees, and the triangle solver for other combinations of sides and angles. Some side-side-angle inputs fit two different triangles, so inspect both solutions.
How do I find the distance or slope between two points?
Use the coordinate geometry calculator when your measurements are points rather than side lengths. It gives the distance, midpoint and slope, and the equation of the line through the points.