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Rectangle Calculator: Area, Perimeter & Diagonal
Choose any two known measurements. The rectangle, results and worked steps update as you type.
Choose any two known measurements. The rectangle, results and worked steps update as you type.
Dimensions
Live geometry diagram
Side ratio (longer:shorter)1.67 : 1
The diagram uses the calculated side ratio.
Results
How it was calculated
When neither side is named, the longer side is shown as length. Rotating the rectangle swaps length and width.
How to use the rectangle calculator
Choose a pair of known measurements, enter both values and select a length unit. All ten distinct pairs are supported; results update immediately.
Geometry formulas
A = l × w
P = 2(l + w)
d = √(l² + w²)
When neither side is named, the longer side is shown as length. Rotating the rectangle swaps length and width.
When is a pair possible?
A diagonal must exceed either side. Area and perimeter require P² ≥ 16A; area and diagonal require d² ≥ 2A; perimeter and diagonal require P/(2√2) ≤ d < P/2.
Rectangle Calculator: Area, Perimeter & Diagonal
How to use the rectangle calculator
Choose a pair of known measurements, enter both values and select a length unit. All ten distinct pairs are supported; results update immediately.
When is a pair possible?
A diagonal must exceed either side. Area and perimeter require P² ≥ 16A; area and diagonal require d² ≥ 2A; perimeter and diagonal require P/(2√2) ≤ d < P/2.
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