How it works
Find the area, perimeter and diagonal of a rectangle using perpendicular length and width in the same unit.
A = ab; P = 2(a+b); d = √(a²+b²)
Worked example
Show example inputs and result
Length: 8 · Width: 5.
- Area
- 40
- Perimeter
- 26
- Diagonal
- 9.43398113
Questions and answers
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy