How is a square different?

A square is simply a rectangle where length equals width.

Rectangle Area & Perimeter Calculator

Calculate the area, perimeter, and diagonal length of a rectangle given its length and width.

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Formula

Area = l×w, Perimeter = 2(l+w), Diagonal = √(l²+w²)

Circle and Triangle Area Formulas, Explained With Real Shapes

The area formulas for circles and triangles (including Heron's formula) worked through with real numbers.

Triangle Area Calculator

Calculate a triangle's area from three side lengths using Heron's formula.

Circle Area & Circumference Calculator

Calculate the area, circumference, and diameter of a circle from its radius.

Percentage Calculator

Find what percentage one number is of another, or calculate percentage change.

Percentage Change Calculator

Calculate the percentage increase or decrease between two values.

Quadratic Equation Solver

Solve ax² + bx + c = 0 for real roots using the quadratic formula.

Average (Mean) Calculator

Calculate the average of up to 10 numbers.