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Perimeter

Formulas for rectangle, square, and triangle — plus an online practice trainer.

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Perimeter — Key Formulas

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Frequently Asked Questions

What is perimeter?

Perimeter is the total length of the boundary of a flat shape — the sum of all its side lengths.

What is the formula for the perimeter of a rectangle?

P = 2(a + b), where a and b are the side lengths.

What is the formula for the perimeter of a square?

P = 4a, where a is the side length.