Revising surface area the night before an exam? These are condensed revision notes — the facts, formulas and mistakes examiners actually mark, with no long explanations. Prefer a full walkthrough with step-by-step reasoning instead? Search “Surface area GCSE” on the site for the complete guide.
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Key facts to remember
1Surface area of a cuboid = 2(lw + lh + wh).
2Surface area of a cylinder = 2πr² + 2πrh (two circular ends + curved surface).
3Surface area of a triangular prism = sum of the two triangular faces + three rectangular faces.
4Nets help visualise surface area — unfold the shape and find the total area.
5Units are always square units (cm², m²).
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Formulas
Cuboid
SA = 2(lw + lh + wh)
Cylinder
SA = 2πr² + 2πrh
Curved surface = 2πrh; each end = πr²
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Worked examples
Example 1
Find the surface area of a cuboid with length 5 cm, width 3 cm and height 4 cm.
Working
Top and bottom: 2 × (5 × 3) = 30
Front and back: 2 × (5 × 4) = 40
Left and right sides: 2 × (3 × 4) = 24
Total = 30 + 40 + 24 = 94 cm²
Answer94 cm²
Example 2
Find the surface area of a cylinder with radius 4 cm and height 10 cm. Give your answer in terms of π.
Working
Two circular ends: 2 × π × 4² = 32π
Curved surface: 2 × π × 4 × 10 = 80π
Total = 32π + 80π = 112π cm²
Answer112π cm²
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Common mistakes
✗Forgetting pairs of faces — each face of a cuboid appears twice (top/bottom, front/back, sides).
✗Confusing surface area with volume.
✗Only finding the curved surface of a cylinder and forgetting the two circular ends.
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Exam tips
✓Sketch the net of the shape to identify all faces before calculating.
✓Check you have the right number of faces — a cuboid has 6, a triangular prism has 5.
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