When to use this calculator
Find the area of a rectangle from its length and width. Both dimensions must use the same unit.
Explore the quadrilateral & polygon calculators for other questions in this topic. For a related calculation, use the Rectangle Perimeter Calculator: Find the total length of the four sides of a rectangle.
PUTTING IT INTO PRACTICE
Rectangle Area: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Length | 8 |
| Width | 5 |
| Result | 40 square units |
- Check the input labels and enter the example values above.
- Apply the relationship: Area = length × width.
- The result is 40 square units, rounded for display.
How to interpret your result
Both dimensions must use the same unit.
A perimeter measures the outline; area measures the enclosed surface. Regular polygon tools assume equal sides and angles. For a parallelogram or trapezoid, use the height perpendicular to the selected base.
Frequently asked questions
What does regular polygon mean?
It is a polygon with all sides equal and all interior angles equal.
How do I use the rectangle area calculator?
Enter length, width. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Area = length × width.
What should I check before using the result?
Both dimensions must use the same unit.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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