Centimeters to Inches (cm → in) – Exact Formula, Examples, Quick Table & FAQ
Convert centimeters to inches. The relationship is exact: 1 inch = 2.54 centimeters. To go from centimeters to inches divide by 2.54. This guide gives you the formula, quick reference values, worked examples, and answers to common questions.
1. Core Idea
Because 1 inch was internationally defined as exactly 2.54 cm, there is no rounding in the factor. Thus: inches = centimeters ÷ 2.54.
2. Conversion Formula
in (inch) = cm ÷ 2.54
cm = in × 2.54
3. Quick Values
1 cm = 0.3937 in
5 cm = 1.9685 in
10 cm = 3.9370 in
15 cm = 5.9055 in
20 cm = 7.8740 in
25 cm = 9.8425 in
30 cm = 11.8110 in
50 cm = 19.6850 in
4. Step‑by‑Step Example
Convert 68 cm to inches
- Write the formula: inches = cm ÷ 2.54
- Insert the value: inches = 68 ÷ 2.54
- Calculate: 68 ÷ 2.54 = 26.7717 in
Answer: 68 cm ≈ 26.7717 inches
5. Practical Uses
- Clothing & body measurements (international size charts).
- Display sizes (screens, frames, tools) often quoted in inches.
- DIY & hardware: Tools labeled in inches vs. metric project plans.
- Science & education: Converting historical data sets.
6. Accuracy & Tips
- The 2.54 factor is exact; rounding only comes from your chosen decimal places.
- Fast mental check: cm ÷ 2.5 then subtract about 1%. Example: 20 cm → 8 − 0.08 ≈ 7.92 (exact 7.8740).
- For feet & inches from cm: total inches = cm ÷ 2.54, then split into feet (÷12) and remainder.
- Keep 2–3 decimals for everyday use; more for technical precision.
7. More Examples Table
| cm | inches (in) |
|---|
| 5 | 1.9685 |
| 8 | 3.1496 |
| 12 | 4.7244 |
| 25 | 9.8425 |
| 40 | 15.7480 |
| 55 | 21.6535 |
| 70 | 27.5591 |
| 90 | 35.4331 |
8. FAQ
- Is 2.54 exact? Yes—set by international agreement in 1959.
- How many inches in 100 cm? 100 ÷ 2.54 = 39.3701 inches.
- Why use inches? Legacy usage in the US and some product industries worldwide.
- Best rounding? For body measurements 1 or 2 decimals is enough.