Length Converter — Cm ↔ Inches

Divide centimeters by 2.54 to get inches. The formula is exact, not approximate — under the 1959 International Yard and Pound Agreement, 1 inch equals exactly 2.54 cm. Example: 30 cm ÷ 2.54 = 11.811 inches exactly.

Multiply inches by 2.54 to get centimeters. Example: 12 inches × 2.54 = 30.48 cm (1 foot exactly). The 2.54 factor is the internationally defined constant, maintained by the BIPM and adopted by all English-speaking nations in 1959.

170 cm equals 5′ 6.93″ (5 feet 6.93 inches, or 66.93 inches total). This is near the global average adult male height of 171 cm per the NCD Risk Factor Collaboration (Lancet, 2020).

6 feet equals exactly 182.88 cm (72 inches × 2.54). This is a major adult male height milestone — men 6 feet or taller are in the top 15% of US adult males per CDC data, and the top 10% globally.

A 55-inch TV is 139.7 cm measured diagonally (55 × 2.54). At 16:9 aspect ratio, the screen dimensions are approximately 121.7 cm wide × 68.4 cm tall. SMPTE recommends a viewing distance of 2.1–3.4 m for a 55-inch 4K TV.

Before 1959, several slightly different inches existed. The International Yard and Pound Agreement of 1959 defined the international inch as exactly 25.4 mm (2.54 cm), adopted by the US, UK, Canada, Australia, New Zealand, and South Africa. This ended centuries of small discrepancies between national inch definitions.

Centimeters are metric (1/100 of a meter) and used in most countries worldwide including all of Europe, Asia, and Latin America. Inches are part of US customary and imperial systems, used primarily in the US, UK, and Canada (for construction and DIY). 1 inch = 2.54 cm exactly, so inches are larger units.

Divide by 2.5 instead of 2.54 — the estimate will be 1.6% low. For 100 cm, 100 ÷ 2.5 = 40 in (exact: 39.37 in). For quick height conversion, remember: 150 cm ≈ 4′ 11″, 160 cm ≈ 5′ 3″, 170 cm ≈ 5′ 7″, 180 cm ≈ 5′ 11″, 190 cm ≈ 6′ 3″.