Geometry calculators
22 free tools
Area, perimeter, volume, and surface area for the shapes that come up most — circles, rectangles, triangles, and the round and boxy solids in between. Each tool shows the formula so you can follow the math yourself.
Find the arc length of a circle from a radius and central angle, plus the sector area and chord.
Enter a radius to get a circle's area, circumference, and diameter from the standard formula.
Calculate a cone's volume from its radius and height, plus slant height and surface area.
Enter a side length to get a cube's volume, surface area, and corner-to-corner space diagonal.
Type in a radius and height to get a cylinder's volume and total surface area.
Calculate an ellipse's area from its two semi-axes, plus its approximate circumference.
Find a regular hexagon's area, perimeter, and long and short diagonals from its side length.
Find a regular octagon's area, perimeter, width across flats and corners, and apothem from its side length.
Calculate a parallelogram's area from base and height, or from two sides and their angle.
Find a regular pentagon's area, perimeter, and diagonal from its side length.
Compute the volume and surface area of a square pyramid from its base edge and height.
Solve a right triangle: the hypotenuse from two legs, or a missing leg from a leg and the hypotenuse.
Type in length and width to find a rectangle's area, perimeter, and corner-to-corner diagonal.
Find a rectangular prism's volume, surface area, and space diagonal from its length, width, and height.
Find a regular polygon's interior angle, perimeter, and area from its number of sides and side length.
Find a rhombus's area, side length, perimeter, and height from its two diagonals.
Give two sides of a right triangle to find the third side, both acute angles, and the area.
Enter a radius to get a sphere's volume and surface area using the 4/3 pi r cubed formula.
Calculate the surface area of a sphere, cube, cylinder, or cone from its dimensions.
Calculate the area of a trapezoid from its two parallel sides and its height.
Find a triangle's area from base and height, or from its three sides using Heron's formula.
Find a triangle's perimeter and its area with Heron's formula from three side lengths.
Frequently asked questions
Do these calculators use any particular units?
They're unit-free, so whatever you type in comes back out. Feed in centimeters and areas come out in square centimeters, volumes in cubic centimeters. Just keep every length in the same unit.
Which geometry tool gets used the most?
The Circle Calculator, usually. Once you have a radius, area and circumference follow in one step. Rectangle area and the Pythagorean theorem are close behind for everyday measuring jobs.
How precise are the results?
Answers are rounded to four decimal places, which is plenty for schoolwork and most projects. Anything using π, like circles and spheres, carries the full value internally before that final rounding.