The formula
in² = cm² × 0.15500031
Where the factor comes from — each unit by its definition, then its size in SI:
1 cm² = cm² = 0.0001 m²1 in² = in² = 0.00064516 m²
Dividing the two SI sizes gives the factor: 0.155000310001 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 6.4516.
Area in SI is the square metre. Squaring a length conversion squares its factor: 1 ft = 0.3048 m, so 1 ft² is 0.3048² m².
Worked examples
- A shoe sole (0.02 m²): 200 cm² = 31.0001 in² — 200 × 0.15500031 = 31.0001
- A gauge face: 6.4516 cm² = 1 in² — 6.4516 × 0.15500031 = 1
- A small room (10 m²): 100,000 cm² = 15,500 in² — 100,000 × 0.15500031 = 15,500
Frequently asked questions
How many square inches is 1 cm²?
1 cm² = 0.155000310001 in².
How do I convert square inches back to square centimetres?
Divide by 0.155000310001 — or multiply by 6.4516: 1 in² = 6.4516 cm².