Difference Between Lateral Surface Area (LSA) and Total Surface Area (TSA)
When we talk about surface area, we mean the total area covered by the outside of a 3D object.
But there are two types:
✅ Lateral Surface Area (LSA)
✅ Total Surface Area (TSA)Let’s understand in a very simple way 👇
Lateral Surface Area (LSA)
📘 Definition:
Lateral Surface Area means the area of the side surfaces only.
👉 It does NOT include the top and bottom.
🎯 Simple Idea:
Think of removing the roof and base — only the walls remain.
🏠 Practical Example 1: Room
Imagine you want to paint only the four walls of your room.
You will NOT paint:
The floor
The ceilingThat painted area = Lateral Surface Area
📦 Practical Example 2: Box Without Top & Bottom
If you remove the top and bottom of a box, the area of the remaining sides is the LSA.
Total Surface Area (TSA)
📘 Definition:
Total Surface Area means the area of all surfaces together.
👉 It includes:
Top
BottomAll side surfaces
🏠 Practical Example 1: Wrapping a Gift Box
When you wrap a gift completely with paper, you cover:
Top
BottomAll sides
That covered area = Total Surface Area
Easy Comparison Table
| Feature | Lateral Surface Area (LSA) | Total Surface Area (TSA) |
|---|---|---|
| Includes side walls? | ✅ Yes | ✅ Yes |
| Includes top? | ❌ No | ✅ Yes |
| Includes bottom? | ❌ No | ✅ Yes |
| Real-life example | Painting room walls | Wrapping full gift box |
Formulas (Cube & Cuboid)
For Cube (side = a)
LSA = 4a²
TSA = 6a²👉 Why?
Cube has 6 faces.
LSA includes only 4 side faces.
TSA includes all 6 faces.
For Cuboid (length = l, breadth = b, height = h)
LSA = 2h(l + b)
TSA = 2(lb + bh + hl)Numerical Example
Example: Cube of side 5 cm
LSA = 4a²
= 4 × 25
= 100 cm²
TSA = 6a²
= 6 × 25
= 150 cm²
👉 Difference = 50 cm² (top + bottom area)
🔥 Quick Trick for Exams
If question says:
"Area of four walls" → LSA
"Area of walls, ceiling and floor" → TSA"Area to wrap completely" → TSA
"Area to paint only sides" → LSA
One-Line Summary
👉 LSA = Only sides
👉 TSA = Entire outer surface