Area, right triangles, circles, rectangles, slopes, distances and common coordinate-geometry formulas. Use the calculators for your own measurements and the guides for worked examples.
Use the tool that matches the exact problem you need to solve.
Calculate area for a rectangle, triangle, circle or trapezoid from the dimensions you enter.
Find the hypotenuse of a right triangle from the two perpendicular side lengths.
Solve a right triangle from two side lengths and find the hypotenuse, angles, area and perimeter.
Calculate triangle area using a base and perpendicular height.
Find the slope of the line through two coordinate points.
Calculate straight-line distance between two points on a 2D coordinate plane.
Find the midpoint between two points on a coordinate plane.
Calculate circumference and area from a circle radius.
Calculate area, perimeter and diagonal of a rectangle from length and width.
Solve a quadratic equation in the form ax² + bx + c = 0 and identify real or complex roots.
Calculate cone volume, slant height and total surface area from radius and vertical height.
Calculate the volume and total surface area of a right circular cylinder.
Calculate the volume and surface area of a sphere from its radius.
10 focused guides and worked examples for this calculator cluster.
Learn the triangle perimeter formula, see a worked example and check whether three side lengths can form a valid triangle.
Read guide →Geometry & TrianglesFind a missing leg of a right triangle when the hypotenuse and the other leg are known.
Read guide →Geometry & TrianglesFind a missing side of a right triangle using the Pythagorean theorem and the two side lengths you already know.
Read guide →Geometry & TrianglesFind an unknown acute angle in a right triangle using sine, cosine or tangent.
Read guide →Geometry & TrianglesLearn the slope formula from two coordinate points and recognize positive, negative, zero and undefined slope.
Read guide →Geometry & TrianglesLearn the base-times-height formula for triangle area and how to use perpendicular height correctly.
Read guide →Geometry & TrianglesLearn the hypotenuse formula and calculate the longest side of a right triangle from the two legs.
Read guide →Geometry & TrianglesLearn how to use a²+b²=c² to find the hypotenuse or a missing leg of a right triangle. See formulas, worked examples and related free calculators.
Read guide →Geometry & TrianglesCalculate the area of a right triangle by multiplying the two perpendicular legs and dividing by two.
Read guide →Geometry & TrianglesUnderstand the legs, hypotenuse and side relationships in a right triangle before choosing a formula.
Read guide →This topic connects general area formulas with shape-specific geometry tools. Use the Area Calculator for rectangles, triangles, circles and trapezoids, then move into dedicated triangle, circle, rectangle, slope and coordinate-geometry calculators when you need more detail.
Use the examples as reference points, then open a calculator and substitute your own values. For decisions involving contracts, taxes, health, payroll rules, construction requirements or other high-stakes details, verify the real-world assumptions with an appropriate authoritative source.
Continue into another connected area of the reference library.