Rectangle Calculator
Enter any two of a rectangle's length, width, area, perimeter and diagonal to find the rest.
Change the values and press Calculate to work out your own figures.
Enter any two of the length, width, area, perimeter and diagonal.
Show the working
- From the length and width: length 3, width 4
- A = l w, P = 2(l + w), d = √(l² + w²)
- Area = 12
How to use it
Enter any two of the length, width, area, perimeter and diagonal.
Enter the measurements (decimals, fractions such as 3/4, or mixed numbers such as 1 1/2) and, if you like, their unit; the answer is then also given in other units. Show the working gives the formula.
Key facts
A = l w; P = 2(l + w); d = √(l² + w²)
From area and perimeter
l and w are the two roots of t² − (P/2)t + A = 0, so they exist only if (P/2)² ≥ 4A.
Questions
What is the diagonal of a 3 × 4 rectangle?
5.
Which rectangle has area 12 and perimeter 14?
4 × 3.
Formulas
A = l w; P = 2(l + w); d = √(l² + w²)
Sources
Limitations
- All measurements in one calculation use the same unit; the answer is also given in other units.
- Measurements up to 10¹⁵.