Core answer: 1 inch = 2.54 cm exactly; 1 foot = 30.48 cm; 1 mile = 1.609 km; 1 m = 3.281 ft. China's traditional units: 1 尺 (chi) = 1/3 m = 33.33 cm, 1 寸 (cun) = 3.33 cm — so a 5尺8 person (like in novels) is 1.93 m in modern metric, and "腰围2尺2" is a 73 cm waist.
The conversion tables you need
| Imperial | Metric | Metric | Imperial |
|---|---|---|---|
| 1 inch | 2.54 cm | 1 cm | 0.394 in |
| 1 foot (12 in) | 30.48 cm | 1 m | 3.281 ft |
| 1 yard (3 ft) | 0.9144 m | 1 km | 0.621 mi |
| 1 mile | 1.609 km | 1 m | 1.094 yd |
| 市制 | Metric | Common use |
|---|---|---|
| 1 寸 | 3.33 cm | waist sizes, photo sizes |
| 1 尺 (10 寸) | 33.33 cm | fabric, height (historical) |
| 1 丈 (10 尺) | 3.33 m | land, literature |
| 1 里 | 500 m | distances ("千里") |
Worked examples
Example 1 — TV sizes. A "65-inch TV" is the diagonal: 65 × 2.54 = 165 cm diagonal; a 16:9 panel measures ≈ 144 × 81 cm — measure your cabinet's width, not the marketing number.
Example 2 — Buying trousers online. Waist 2尺3 = 23 × 3.33 ≈ 76.6 cm ≈ 30 inches. The same person wears "30" in US jeans.
Example 3 — Marathon. 42.195 km = 26.2 miles; a 5:00/km pace is an 8:03/mile pace.
Example 4 — Height in the US. 175 cm = 175/2.54 = 68.9 in = 5 ft 8.9 in — say "five nine".
Common mistakes and myths
- Confusing 市寸 with 英寸 — a "7寸 photo" (Chinese cun, 12.7×17.8 cm) is a "5R/7-inch photo" (17.8 cm diagonal-ish naming); different cun!
- Nautical vs statute miles — 1 nautical mile = 1.852 km (aviation/shipping), not 1.609; knots are nautical miles per hour.
- Assuming US and UK miles differ — they don't; but UK pints/gallons DO differ from US (see volume guide).
- Forgetting historical 尺 differs — the Qing dynasty 尺 was 32 cm, Tang 30.7 cm; "身高八尺" in ancient texts is NOT 2.67 m — it's ~1.85 m on the period's ruler.
- Mixing up fabric 尺 with body 尺 — tailors still measure in 市尺; bring the 33.33 factor, not 30.48.