Geometry

Geometry calculators with diagrams: circle, rectangle, triangle area, the Pythagorean theorem, and slope.

This hub gathers the shape and coordinate-geometry tools, each with a clear diagram. Find areas, perimeters, a hypotenuse, or the slope of a line.

Use the circle and rectangle calculators for area and perimeter, the triangle area calculator (base-height or Heron’s formula), the Pythagorean theorem for right triangles, and the slope calculator for the gradient of a line.

Calculators Circle Calculator Find a circle's radius, diameter, circumference, and area from any one of them. Shows the formulas. Calculators Rectangle Calculator Find the area, perimeter, and diagonal of a rectangle from its length and width. Shows the formulas. Calculators Triangle Area Calculator Find the area of a triangle from its base and height, or from its three sides with Heron's formula. Calculators Pythagorean Theorem Calculator Find the hypotenuse or a missing leg of a right triangle using the Pythagorean theorem. Shows the steps. Calculators Slope Calculator Find the slope of a line through two points, plus the line equation. Shows rise over run and the steps. Calculators Distance and Midpoint Calculator Find the distance between two points and their midpoint, with the formulas and steps. Calculators Volume Calculator Find the volume of a box, cube, sphere, cylinder, or cone. Shows the formula and the steps. Calculators Surface Area Calculator Find the surface area of a box, cube, sphere, cylinder, or cone. Shows the formula and the steps. Calculators Square Root Calculator Find the square root of a number as a decimal, plus the simplified radical form for whole numbers. Shows the steps.

Frequently asked questions

How do you find the area of a circle, rectangle, or triangle?

Circle: π × r². Rectangle: length × width. Triangle: ½ × base × height (or Heron’s formula from three sides). Each calculator shows the steps.

What is the Pythagorean theorem?

For a right triangle, a² + b² = c², where c is the hypotenuse. Use it to find a missing side.

How do you find the slope of a line?

Slope is rise over run: (y2 − y1) / (x2 − x1). The slope calculator also gives the line equation.