About this Rectangle Calculator
Rectangle Calculator returns three useful geometry results together: area, perimeter and corner-to-corner diagonal.
Formula or method
Area = L×W; Perimeter = 2(L+W); Diagonal = √(L²+W²).
Example
A 6 by 8 rectangle has area 48, perimeter 28 and diagonal 10.
Common uses
- Estimate floor or wall area.
- Calculate border length.
- Check diagonal measurements for layout work.
How to use this tool
- Enter the values or text requested by the calculator.
- Choose units or options when the tool provides them.
- Select the calculation button and review the result.
- Use the formula, example and notes on this page to check whether the result fits your situation.
Important note
Use the same measurement unit for length and width.
Frequently asked questions
Is a square supported?
Yes. Enter the same number for length and width.
What unit is the area in?
Area is expressed in the squared version of the input unit.