Math
Geometry Calculator
Area, perimeter, volume, and surface area for common shapes.
Select a shape above
Enter all three sides — area uses Heron's formula.
Formula
2D Shape Formulas
| Shape | Area | Perimeter |
|---|---|---|
| Circle | πr² | 2πr |
| Square | s² | 4s |
| Rectangle | w×h | 2(w+h) |
| Triangle (Heron) | √(s(s-a)(s-b)(s-c)) | a+b+c |
| Trapezoid | ½(a+b)h | a+b+c+d |
| Parallelogram | b×h | 2(b+s) |
3D Shape Formulas
| Shape | Volume | Surface Area |
|---|---|---|
| Sphere | (4/3)πr³ | 4πr² |
| Cube | s³ | 6s² |
| Box | l×w×h | 2(lw+lh+wh) |
| Cylinder | πr²h | 2πr(r+h) |
| Cone | (1/3)πr²h | πr(r+l) |
Cone: l = slant height = √(r²+h²)
Unit Conversions
FAQ
Frequently asked questions.
What can a geometry calculator compute?
A geometry calculator can compute a wide range of measurements including area, perimeter, volume, surface area, angles, and side lengths for both 2D and 3D shapes. It covers plane geometry (triangles, circles, rectangles, polygons) and solid geometry (spheres, cylinders, cones, cubes). Many tools also handle trigonometric functions like sine, cosine, and tangent to solve angle and side problems.
How do I calculate the area of a triangle online?
To calculate the area of a triangle, you can use the base-times-height formula: Area = (1/2) x base x height. If you only know the three side lengths, the Heron's formula approach works without needing the height. An online geometry calculator lets you enter whichever measurements you have and instantly outputs the area along with the formula used.
Can I use a geometry calculator for 3D shapes like cylinders and spheres?
Yes, a solid geometry calculator handles 3D shapes including cylinders, spheres, cones, cubes, rectangular prisms, and pyramids. You can compute volume, total surface area, and lateral surface area by entering the required dimensions such as radius, height, or side length. Results are shown with formulas so you can follow along and learn the underlying math.
How do I find the perimeter of a shape using a calculator?
To find the perimeter, enter the shape type and its dimensions — for example, side lengths for a polygon or the radius for a circle (which gives you the circumference). The calculator applies the correct formula automatically and returns the perimeter instantly. For irregular shapes, you can sum individual side lengths using the calculator's addition tool.
What is the difference between plane geometry and solid geometry?
Plane geometry deals with flat, two-dimensional shapes such as triangles, circles, squares, and polygons, measuring properties like area, perimeter, and angles. Solid geometry covers three-dimensional figures like spheres, cones, and prisms, where the key measurements are volume and surface area. An online geometry calculator typically supports both categories, letting you switch between 2D and 3D calculations in one place.
How do I calculate angles in a right triangle using trigonometry?
In a right triangle, you can find unknown angles using the trigonometric ratios: sine (opposite/hypotenuse), cosine (adjacent/hypotenuse), and tangent (opposite/adjacent). Enter two known values — such as two side lengths — into a geometry calculator and it will compute the missing angles and sides. The inverse functions (arcsin, arccos, arctan) are used when you know a ratio and need the angle in degrees.
Is this geometry calculator free to use?
Yes, this geometry calculator is completely free to use with no registration or download required. It runs entirely in your browser and supports a wide variety of shapes and formulas for both plane and solid geometry. All results include the formula and step-by-step working so you can understand the calculation, not just the answer.
Last updated: August 17, 2026