Imagine you are taking a fun morning walk right along the edge of your school playground. The total distance you cover from start to finish as you go all the way around is called its PERIMETER!
We strictly measure the outer fence or border line, never the middle area!
Perimeter only exists for fully closed figures (no open ends!).
Perimeter is the length of fence; Area is the grass inside the yard!
We use perimeter every single day! Here are 10 super cool examples:
The total wire length needed to build a safety fence around a cozy yard.
The decorative wooden trim that runs all around the edge of a door.
The running path drawn right around the boundary of the school grounds.
The colorful tape ribbon glued around the outer trim of your notebook.
The wooden or plastic border holding your family picture together.
The non-slip safety tile border laid around the water's edge.
The small brick border built to keep flower beds tidy and pretty.
The rubber sealant strip lining the frame to keep rainwater out.
The protective bumper case wrapping around the edges of a smartphone.
The decorative skirting board tiles fitted along the bottom of room walls.
Look at this colorful rectangle. Let's name its key parts:
"PERI" means Around | "METER" means Measure
So, Perimeter literally means "Measuring All Around!"
🤖 Funny Cartoon Rule:
"Area is the Grass to mow 🌱, Perimeter is the Fence around it, yo! 🛑"
Finding perimeter is as easy as 1-2-3! Just follow these steps:
Identify all outer straight boundary lines of the closed figure.
Find or read the lengths given for each side (e.g., in cm, meters, inches).
Sum up every single side length: Perimeter = Sum of All Sides
Smart shortcut formulas to calculate perimeter fast!
Since opposite sides are equal, add Length + Length + Breadth + Breadth:
Example: If L = 8 and B = 5, then P = 2 × (8 + 5) = 26 units.
Since all 4 sides are exactly equal, multiply 1 side length by 4:
Example: If Side = 7 cm, then P = 4 × 7 = 28 cm.
A triangle has 3 sides. Simply add all three side lengths together:
Example: If sides are 5 cm, 6 cm, 8 cm: P = 5 + 6 + 8 = 19 cm.
Count and add up every single outer line segment!
Click on any example below to reveal the step-by-step solution!
Question: Find the perimeter of a rectangle with Length = 8 cm and Breadth = 5 cm.
Step 1: Identify the formula: P = 2 × (Length + Breadth)
Step 2: Add Length and Breadth: 8 + 5 = 13 cm
Step 3: Multiply by 2: 2 × 13 = 26 cm
✅ Answer: Perimeter = 26 cm
Question: Calculate perimeter of a square tile with Side = 7 cm.
Step 1: Formula for Square: P = 4 × Side
Step 2: Multiply: 4 × 7 = 28 cm
✅ Answer: Perimeter = 28 cm
Question: Find the perimeter of a triangle with sides measuring 5 cm, 6 cm, and 8 cm.
Step 1: Formula: P = Side 1 + Side 2 + Side 3
Step 2: Add all 3 sides: 5 + 6 + 8 = 19 cm
✅ Answer: Perimeter = 19 cm
Question: A park has length 10 m and breadth 4 m. What is its perimeter?
Solution: P = 2 × (10 + 4) = 2 × 14 = 28 m
✅ Answer: Perimeter = 28 m
Question: Find the length of fence needed for a square garden with side 15 m.
Solution: P = 4 × 15 = 60 m
✅ Answer: Perimeter = 60 m
Never mix these two up again! Here is how they compare:
| Feature | 🟩 AREA | 🔴 PERIMETER |
|---|---|---|
| What it measures | Inside surface / region space | Outside boundary / edge distance |
| Units | Square units (cm², m²) | Standard linear units (cm, m) |
| Real-life Example 1 | Floor carpet / tiles needed | Wooden skirting border around floor |
| Real-life Example 2 | Painting a bedroom wall | Ribbon along the edges of a picture |
| Real-life Example 3 | Lawn grass coverage | Fencing wire around the garden |
We measure perimeter using linear metric units depending on the size of the object:
Used for tiny objects: Stamps, coins, eraser borders, small bug paths.
Used for medium objects: Notebooks, pencil boxes, photos, phone screens.
Used for large objects: Classroom boundaries, swimming pools, gardens, yards.
Used for huge distances: City boundaries, marathon tracks, large farm fields.
A goat is tied with a rope to a fence post and walks all the way around the outside edge of a square field. Does the rope track measure Area or Perimeter?
Answer: PERIMETER! Because the goat is walking strictly along the outside boundary of the field.
Q1: If you double all side lengths of a square, what happens to its perimeter?
👉 It doubles as well!
Q2: Can two shapes have different areas but the exact same perimeter?
👉 Yes! (e.g., 4 × 4 square vs 6 × 2 rectangle both have P = 16).
Q3: A wire of length 20 cm is bent to make a square. What is each side length?
👉 20 ÷ 4 = 5 cm.
Q4: Do we count internal walls when calculating house perimeter?
👉 No! Only the outer exterior walls count.
Q5: An equilateral triangle has P = 27 cm. How long is one side?
👉 27 ÷ 3 = 9 cm.
Q6: Why do we measure perimeter in cm instead of cm²?
👉 Because perimeter measures 1D length, not 2D surface area.
Q7: A rectangle has P = 30 cm and Length = 10 cm. What is Breadth?
👉 30 ÷ 2 = 15, Breadth = 15 - 10 = 5 cm.
Q8: A runner completes 2 laps around a 50 m × 30 m field. Total distance?
👉 1 Lap = 2 × (50 + 30) = 160 m. 2 Laps = 320 m.
Q9: What shape gives the largest area for a fixed perimeter?
👉 A Circle!
Q10: If a shape is open on one side, can we find its perimeter?
👉 No, perimeter requires a fully closed figure.
1. 🌳 Garden Fence: A square garden has a side length of 12 m. How many meters of wire fence are required to enclose it?
Sol: P = 4 × 12 = 48 meters.
2. 🏫 School Playground: A rectangular playground is 25 m long and 15 m wide. A student runs around it once. How far did they run?
Sol: P = 2 × (25 + 15) = 2 × 40 = 80 meters.
3. 📚 Book Lace: Tina wants to put a golden lace along the border of her math book (20 cm × 15 cm). How much lace is needed?
Sol: P = 2 × (20 + 15) = 70 cm.
4. 🪟 Window Frame: A square window frame has a side of 90 cm. What is its total outer perimeter?
Sol: P = 4 × 90 = 360 cm (or 3.6 meters).
5. 🖼️ Picture Frame: A triangular photo frame has sides 12 cm, 15 cm, and 18 cm. Find its perimeter.
Sol: P = 12 + 15 + 18 = 45 cm.
6. 🏊 Swimming Pool: A pool measures 30 m in length and 12 m in width. Find the total tile border length.
Sol: P = 2 × (30 + 12) = 84 m.
7. 🎁 Ribbon Box: Sam wraps ribbon around a gift box top of dimensions 18 cm × 10 cm. How much ribbon is used?
Sol: P = 2 × (18 + 10) = 56 cm.
8. 🛣️ Park Path: A triangular park has sides 100 m, 150 m, and 120 m. Find the length of the walking track around it.
Sol: P = 100 + 150 + 120 = 370 m.
9. 🏫 Classroom Display: A bulletin board is 4 m long and 2 m high. How much wooden border tape is needed?
Sol: P = 2 × (4 + 2) = 12 meters.
10. 🧱 Skirting Board: A square room has a side of 6 m. How long is the floor border skirting needed (ignoring the door)?
Sol: P = 4 × 6 = 24 meters.
11. ⚽ Football Pitch: A football field is 100 m long and 60 m wide. Calculate its total boundary perimeter.
Sol: P = 2 × (100 + 60) = 320 meters.
12. 🏷️ Name Tag: A rectangular name badge is 8 cm long and 5 cm wide. Find its border length.
Sol: P = 2 × (8 + 5) = 26 cm.
13. 🚜 Farmer's Field: A farmer has a triangular plot with sides 45 m, 55 m, and 60 m. Find total fencing needed.
Sol: P = 45 + 55 + 60 = 160 meters.
14. 📱 Tablet Screen: A tablet screen measures 24 cm by 18 cm. Find the perimeter of the screen protector.
Sol: P = 2 × (24 + 18) = 84 cm.
15. 📐 Pentagon Sandbox: A regular 5-sided sandbox has each side measuring 3 meters. Find its perimeter.
Sol: P = 5 × 3 = 15 meters.
Wrong: Counting interior squares or area tiles.
✅ Correct: Only trace and measure the OUTSIDE boundary lines!
Wrong: Adding L + B only once for a rectangle (8 + 5 = 13).
✅ Correct: Add all 4 sides! 2 × (8 + 5) = 26.
Wrong: Writing perimeter as 26 cm².
✅ Correct: Always use linear units like cm, m, mm.
Wrong: Multiplying L × B to find perimeter.
✅ Correct: Multiply is for AREA; Perimeter is SUM of sides!
🚩 OUTSIDE BOUNDARY
📏 DISTANCE AROUND
➕ ADD ALL SIDES
🏃 WALK THE EDGE!
Choose a practice mode to test your perimeter skills!
1. The distance around a closed figure is called its
2. Perimeter of a square with side 6 cm is cm.
3. Formula for perimeter of a rectangle is
4. We measure perimeter in units.
1. What is the perimeter of a rectangle with Length = 10 cm and Breadth = 4 cm?
2. Which unit is best for measuring the perimeter of a garden?
1. Area measures the outside fence of a garden. (True / False)
2. A square with side 5 cm has a perimeter of 20 cm. (True / False)
1. Find perimeter of a triangle with sides 7 cm, 8 cm, and 9 cm.
Can you find the missing side length?
A rectangle has a Perimeter = 30 cm and Length = 10 cm. What is its Breadth?
A triangle has a Perimeter = 25 cm. Two sides are 8 cm and 10 cm. Find the 3rd side!
Engineers calculate school perimeter to estimate brick requirements.
Farmers measure field boundary to buy barbed wire fence rolls.
Carpenters measure picture perimeter to cut wooden frame borders.
Test your complete perimeter knowledge! Score correct points to launch celebratory confetti! 🎉
Q1. Perimeter is the measure of the _______ boundary of a closed shape.
Q2. What is the perimeter of a square with side 8 cm?
Q3. Formula for perimeter of a rectangle with length L and breadth B?
✔ Perimeter = Total distance around the outside boundary.
✔ Always add every outer side together.
✔ Square P = 4 × Side | Rectangle P = 2 × (L + B)
✔ Units are linear (cm, m, km).