Area and Volume Formulas Made Simple
The essential area, perimeter and volume formulas for circles, rectangles, triangles, spheres and cylinders — what they mean, how to handle composite shapes, and how to keep units straight.
Rectangle Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Area
48.00
- Perimeter
- 28.00
- Diagonal
- 10.0000
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Rectangle Calculator
The Rectangle Calculator works out your area, along with 2 related figures in an instant. Enter length and width and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the length.
- Enter the width.
- Read off your area, together with perimeter and diagonal — the calculator updates automatically, with no button to press.
Formula
The Rectangle Calculator uses the formula:
Area = Length × Width
Worked example
For example, with length of 8 units and width of 6 units, the area is 48.00.
| Length | 8 units |
|---|---|
| Width | 6 units |
| Area | 48.00 |
|---|---|
| Perimeter | 28.00 |
| Diagonal | 10.0000 |
Results are estimates for educational use, not professional advice.
Key terms explained
- Perimeter
- The total distance around the outside of a two-dimensional shape.
- Area
- The amount of two-dimensional space a shape covers, measured in square units.
Frequently asked questions
Multiply the length by the width: A = l × w. A rectangle 8 by 6 has an area of 48 square units.
Add the length and width and double the result: P = 2 × (l + w). For 8 by 6 the perimeter is 28 units.
The diagonal uses the Pythagorean theorem: d = √(l² + w²). For 8 by 6 the diagonal is 10 units.
Yes. A square is a rectangle with equal sides, so enter the same value for length and width.
Enter the length. Enter the width. Read off your area, together with perimeter and diagonal — the calculator updates automatically, with no button to press.
Related guides
Rectangle Table: Area by Length
Reference table of area for Rectangle across a range of length values — exact, engine-computed figures you can read off at a glance.
How to Calculate Rectangle: Formula, Steps & Examples
Learn how to calculate Rectangle — the formula explained step by step, with worked examples and a free calculator to check your answer.