Calculate a rectangle’s area, perimeter, diagonal and aspect ratio from its length and width.
100% FreeNo sign-upPrivate — runs in your browser
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Result
Area
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Perimeter
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Diagonal
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Aspect ratio
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Shape
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How to use this tool
1
Enter the lengthUse any unit.
2
Enter the widthUse the same unit as the length.
3
Read area and perimeterThe basic measures.
4
Read diagonal and aspect ratioUseful for screens, frames and layouts.
Formula & worked example
Area = L × W; perimeter = 2(L + W); diagonal = √(L² + W²).
A 3 × 4 rectangle has area 12, perimeter 14 and diagonal 5.
Limitations — read this before you rely on it
Rectangles only; it does not handle parallelograms or irregular quadrilaterals.
Frequently asked questions
Diagonal = √(length² + width²), by Pythagoras’ theorem.
When length equals width.
Length divided by width, shown as a ratio to 1.
Area is square units, perimeter and diagonal are plain units, matching your input.
No — convert both to the same unit first.