Rectangle Perimeter Calculator
Calculate the perimeter and area of a rectangle from width and height.
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How to use this tool
- Enter width and height in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your perimeter and the full breakdown beneath it.
Calculate the perimeter (2×(w+h)) and area (w×h) of a rectangle.
Formula
Perimeter = 2 × (width + height)
Area = width × height
perimeter = 2*(width + height) area = width * height
How it works
This calculator computes both the perimeter and the area of a rectangle from its width and height. The perimeter is the total length of all four sides — two widths plus two heights — while the area is the product of the two dimensions. Both formulas assume right-angle corners; if the shape is not a true rectangle (all 90° angles), results will not be accurate.
Worked example
- Enter width = 5 and height = 3.
- Perimeter: 2 × (5 + 3) = 2 × 8 = 16.
- Area: 5 × 3 = 15.
Perimeter = 16 units; Area = 15 square units.
Common mistakes to avoid
- Computing perimeter as width + height (only two sides) instead of 2 × (width + height).
- Confusing perimeter with area; perimeter is the total border length, area is the enclosed space.
- Using inconsistent units for width and height (e.g. one in cm, one in mm) without converting first.
Key terms
- Perimeter
- The total distance around the outside of a shape — the sum of all side lengths.
- Area
- The amount of two-dimensional space enclosed within the rectangle, in square units.
- Width
- The horizontal dimension of the rectangle.
- Height
- The vertical dimension of the rectangle, also called the length in some conventions.
Frequently asked questions
- How do you find the perimeter of a rectangle?
- Perimeter = 2 × (width + height). Area = width × height.