Inches to Centimeters Formula Explained

4 min read•June 1, 2025•Reviewed: June 1, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 1, 2026

The formula for converting inches to centimeters is cm = in × 2.54 — exact by international definition. In 1959, the US, UK, Canada, Australia, New Zealand, and South Africa agreed that one inch equals exactly 2.54 centimeters. This makes every inch-to-centimeter conversion an exact computation, not an approximation.

This conversion appears constantly in screen sizes, clothing measurements, body height comparisons, and hardware specifications. Inches dominate in the US; centimeters dominate everywhere else.

The Formula

cm = in × 2.54  (exact)

Worked examples:
    1 in × 2.54 =   2.54 cm
    6 in × 2.54 =  15.24 cm
   12 in × 2.54 =  30.48 cm  (= 1 foot)
   24 in × 2.54 =  60.96 cm  (= 2 feet)
   36 in × 2.54 =  91.44 cm  (= 1 yard)
   72 in × 2.54 = 182.88 cm

Converting feet-and-inches to cm:
  Convert all to inches first, then multiply by 2.54
  5 ft 9 in = (5 × 12) + 9 = 69 in × 2.54 = 175.26 cm
  6 ft 2 in = (6 × 12) + 2 = 74 in × 2.54 = 187.96 cm

Why 2.54 Is Exact

The 1959 international yard-and-pound agreement defined 1 yard = 0.9144 meters. Since 1 yard = 36 inches, 1 inch = 0.9144 ÷ 36 = 0.0254 meters = 2.54 centimeters. The value 2.54 is therefore a defined exact value, not derived from physical measurement.

Prior to 1959, slightly different inch definitions existed in different countries (the US survey inch = 2.540005 cm). The 1959 standardization eliminated this discrepancy for most purposes. The US survey inch survives only in some older US land survey records.

Quick Tips

✓
Multiply by 2.5 for a quick estimate — off by only 1.6% (e.g., 10 in × 2.5 = 25 cm vs exact 25.4 cm).
✓
12 in = 30.48 cm — the foot-to-cm conversion derived from this formula.
✓
Screen sizes: TV diagonal in inches × 2.54 = diagonal in cm.
✓
For heights: total the inches first (ft × 12 + remaining inches), then × 2.54.
✓
Common anchors: 1 in = 2.54 cm, 10 in = 25.4 cm, 100 in = 254 cm.