Rectangle & Square Calculator

Enter two side lengths to find area, perimeter, and diagonal for a rectangle or square.

Quick Answer

An 8 by 6 rectangle has area 48 square units and perimeter 28 units. When both sides are equal, the shape is a square.

Area = length × width; perimeter = 2(length + width)

Use positive side lengths in the same unit. Equal sides are treated as a square.

Area
48 square units

Rectangle · perimeter 28 units

Perimeter28 units
Diagonal10 units
ShapeRectangle
Side ratio1.333333
Steps

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    How to Use the Rectangle Calculator

    Enter length and width using the same unit. Choose the unit label if you want a labeled answer. The calculator returns area in square units and perimeter and diagonal in length units. Enter equal values for a square.

    Rectangle and Square Formulas

    Area measures the surface inside the shape. Perimeter measures the distance around it. A diagonal crosses from one corner to the opposite corner and uses the Pythagorean theorem.

    Rectangle: A = L × W; P = 2(L + W); d = √(L² + W²)
    Square: A = s²; P = 4s; d = s√2

    Worked Example: 8 by 6 Rectangle

    Multiply the sides for area: 8 × 6 = 48 square units. Add and double the sides for perimeter: 2(8 + 6) = 28 units. The diagonal is √(8² + 6²) = √100 = 10 units.

    When Is a Rectangle a Square?

    A square is a rectangle whose four sides are equal. If length and width both equal 5 cm, the area is 25 cm² and perimeter is 20 cm. Equal-side detection is based on the values you enter; measurements rounded differently may not compare as exactly equal.

    Keep Length and Area Units Separate

    If both side lengths are in centimeters, the perimeter and diagonal are in centimeters, while area is in square centimeters (cm²). Convert mismatched side units before entering them; otherwise the numeric result will not describe the intended shape.

    Rectangle and Square FAQs

    What is the area of an 8 by 6 rectangle?

    48 square units.

    What is the perimeter of an 8 by 6 rectangle?

    28 units.

    How do I calculate a square?

    Enter the same positive length for both sides.

    Editorial review

    SolverCalc names Prof. Dr. Khalil Mudassar as its educational reviewer. The formulas and examples are documented in the references below.

    Sources

    View references

    Disclaimer

    For educational use. Check your class or textbook convention when the problem defines a different range, sequence index, or notation.