Perimeter of Rectangle: Formula, Examples and Questions

Perimeter of Rectangle is the total distance around a rectangular figure. It is calculated by adding all four sides, or by using 2 × (length + breadth). This page covers the formula, related properties, unit conversions, reverse calculations and solved perimeter of rectangle problems.

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What Is the Perimeter of a Rectangle?

The perimeter of a rectangle is the total length of its boundary. If its length is l and breadth is b, then its perimeter is P = 2(l + b).

A rectangle has two equal lengths and two equal breadths. Therefore, P = l + b + l + b = 2l + 2b = 2(l + b). Perimeter is measured in linear units such as cm, m or km. For a rectangle with length 12 cm and breadth 5 cm, P = 2(12 + 5) = 34 cm.

Perimeter of Rectangle Video Lessons

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Rectangle Area and Perimeter

Learn how to calculate the area and perimeter of a rectangle using the standard formulas, with clear application of length and breadth measurements.

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Perimeter of Rectangle Formula & Tricks

Important Formulas

Basic perimeter formula
P = 2(l + b)

Here, P is the perimeter, l is the length and b is the breadth of the rectangle.

Expanded formula
P = 2l + 2b

This form adds the two equal lengths and the two equal breadths separately.

Length from perimeter
l = P/2 − b

If the perimeter and breadth are known, subtract the breadth from half the perimeter.

Breadth from perimeter
b = P/2 − l

If the perimeter and length are known, subtract the length from half the perimeter.

Quick Tricks

Use the half-perimeter

Since P = 2(l + b), half the perimeter equals l + b. This makes reverse questions faster.

Example: If P = 50 cm and b = 9 cm, then l + b = 25 cm, so l = 25 − 9 = 16 cm.
Convert units before adding

Length and breadth must be in the same unit before applying the formula.

Example: For l = 2 m and b = 50 cm, convert 2 m to 200 cm. Then P = 2(200 + 50) = 500 cm = 5 m.
Remember the equal-side pairs

Do not multiply only length and breadth by two separately without adding them. The correct expression is 2(l + b).

Example: For l = 8 cm and b = 3 cm, P = 2(8 + 3) = 22 cm.

Perimeter of Rectangle Concepts

Applying the Perimeter Formula

Substitute the length and breadth in P = 2(l + b), then simplify the sum before multiplying by 2.

The four sides are l, b, l and b. Thus, the total boundary is l + b + l + b. For l = 15 m and b = 7 m, P = 2(15 + 7) = 44 m.

Example: A rectangular field is 24 m long and 16 m broad. Its perimeter is 2(24 + 16) = 80 m.

Finding a Missing Length or Breadth

When the perimeter is known, use l + b = P/2 to find the missing side.

For a known length, b = P/2 − l. For a known breadth, l = P/2 − b. If P = 72 cm and l = 20 cm, then b = 72/2 − 20 = 16 cm.

Example: A rectangle has perimeter 94 cm and breadth 18 cm. Its length is 94/2 − 18 = 29 cm.

Unit Conversion in Perimeter Questions

Convert all dimensions to one unit before calculating the perimeter.

Use 1 m = 100 cm, 1 km = 1000 m and 1 cm = 10 mm. The answer has the same linear unit as the dimensions used in the calculation.

Example: If l = 3 m and b = 80 cm, then l = 300 cm. Therefore, P = 2(300 + 80) = 760 cm, or 7.6 m.

Perimeter of a Square as a Special Case

A square is a rectangle with equal length and breadth, so its perimeter is 4s.

Putting l = b = s in P = 2(l + b) gives P = 2(s + s) = 4s. A square with side 11 cm has perimeter 4 × 11 = 44 cm.

Example: If a rectangle has equal length and breadth of 9 m, it becomes a square and its perimeter is 4 × 9 = 36 m.

Perimeter of Rectangle Visual Guide

Use the diagram or chart below to understand the concept clearly.

Rectangle with length and breadth

Visual guide: Rectangle with length and breadth
Length: l Breadth: b Perimeter: P = 2(l + b)
The perimeter is the sum of the two equal lengths and two equal breadths.

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Practice Perimeter of Rectangle Questions

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1What is the largest 4 digit number that is divisible by 3, 7, 11, 13 ?→ 2A city has a population of 1 million people. If the population increases at a steady rate of 5% per year, what will the population of the city be after 2 years?→ 3What is the maximum value that must be assigned to A so that the 8-digit number 993A6729 is divisible by 3?→ 4A man loses 20% of his money. He then spends 25% of what remains. If he is left with ₹525, what was his original amount?→ 592 + 58 - 66 + (39 + 24) - 73 + 41 = ?→ 6In a test, Student B scored 20% fewer marks than Student A. If B scored 72 marks, by what percentage did A score more marks than B?→ 7Evaluate: 3⁵ × 7⁵ ÷ 21³→ 8If the marked price of an article is ₹2,400 and the discount is 16%, then the selling price of the article is:→ 9A shop sells towels under an offer where a customer buys 3 towels and gets 2 towels free, all having the same marked price. What is the effective discount percentage the customer receives?→ 10The price of a pen is ₹47. A scheme offers a deal: "Buy 4 and get 50% off on 1." Find the effective price per pen.→

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Quick Revision Notes

Perimeter of Rectangle Revision Points

Use these formulas and rules for quick revision.

  • Perimeter means the total distance around a figure.
  • For a rectangle, P = 2(l + b).
  • A rectangle has two equal lengths and two equal breadths.
  • Half the perimeter equals length plus breadth: P/2 = l + b.
  • Length = P/2 − breadth; breadth = P/2 − length.
  • Use the same unit for length and breadth before calculation.
  • Perimeter is expressed in linear units, not square units.

Related Topic Explainers

Area of Square → Perimeter of Square → Area of Rectangle →

Perimeter of Rectangle FAQs

What is the perimeter of a rectangle with length 18 cm and breadth 7 cm?

P = 2(18 + 7) = 2 × 25 = 50 cm.

How do you find the length when the perimeter is 64 m and breadth is 12 m?

Use l = P/2 − b. Therefore, l = 64/2 − 12 = 32 − 12 = 20 m.

What is the difference between the perimeter and area of a rectangle?

Perimeter measures the boundary and is P = 2(l + b), in linear units. Area measures the enclosed region and is A = l × b, in square units.

What is the perimeter of a rectangle measuring 1.5 m by 80 cm?

Convert 1.5 m to 150 cm. Then P = 2(150 + 80) = 460 cm, which equals 4.6 m.

If the perimeter of a rectangle is 40 cm and its length is 14 cm, what is its breadth?

b = P/2 − l = 40/2 − 14 = 20 − 14 = 6 cm.

What is the perimeter of a rectangle when its length and breadth are equal?

It becomes a square. If each side is s, the perimeter is 4s.

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