Height conversions are often easier to use when the decimal result is translated into whole feet plus remaining inches. The key is to keep the conversion factors separate and avoid rounding before the final step.
The conversion factors
One inch equals 2.54 centimeters, and one foot equals 30.48 centimeters. Decimal feet = centimeters ÷ 30.48.
Worked example: 170 cm
170 ÷ 30.48 = 5.5774 decimal feet. The whole-foot portion is 5 feet. The remainder, 0.5774 feet × 12, is 6.9288 inches, so 170 cm is about 5 ft 6.93 in.
Rounding and display
Keep extra precision until the inches calculation is complete. Round the final inches to the level useful for the context; a medical or product measurement may require a different precision than a casual height reference.
Use the reverse conversion
To convert feet and inches back to centimeters, convert feet to inches, add the remaining inches, then multiply by 2.54. Check both directions when a form or product specification matters.
Sources
The figures and rules in this guide are checked against:
- SI Units: Length — NIST Office of Weights and Measures
- NIST Guide to the SI, Appendix B: Conversion Factors — NIST
- NIST Handbook 44 (Appendix C: General Tables of Units of Measurement) — NIST
- SI base unit: metre — BIPM