Units & Conversion · 英尺与英寸（Foot & Inch） · Updated 2026-10-25
What Is Foot & Inch?
Definition
A foot = 12 inches = 30.48 cm; an inch = 2.54 cm (exact since 1959). Spoken height 5'7" = 67 inches = 170.2 cm. Screen "inches" are diagonal inches; pipe and tire inches are imperial too — colloquial Chinese "寸" almost always means the imperial inch, not the market inch (3.33 cm). US length runs on 12ths and 16ths (feet-inches-fractional inches), where decimal conversion slips most.
Formula
1 in = 2.54 cm; 1 ft = 12 in = 30.48 cm; inches × 2.54 = cm
Worked Example
6'2" = 74 in = 188 cm; a 27-inch display has a 68.6 cm diagonal (~59.8×33.6 cm at 16:9); a 1/2-inch pipe is 12.7 mm (nominal DN15 differs).
Common Misconception
Reading 5'7" as 5.7 feet (=173.7 cm) — the digits after the apostrophe are inches, not decimal feet. And in consumer electronics "cun" is never the market inch (3.33 cm): a "6.7-inch" phone is a 17 cm diagonal, a huge gap if misread.
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