1 inch at a glance
- Centimeters
- 2.54 cm
- Millimeters
- 25.4 mm
- Meters
- 0.0254 m
- Feet & inches
- 1 in (under 1 ft)
- Feet (decimal)
- 0.0833 ft
- Nearest whole cm
- 3 cm
How to convert 1 inch to cm
cm = inches × 2.54
1 × 2.54 = 2.54 cm
1 × 2.54 = 2.54 cm
Because the inch is defined as exactly 2.54 cm, 2.54 cm is exact — no rounding involved. To do it in your head, split 2.54 into 2.5 + 0.04: 1 × 2.5 = 2.5 and 1 × 0.04 = 0.04, which add up to 2.54.
Fractions of an inch around 1 in
Tape measures between 1 and 2 in are marked in eighths. Each eighth adds 3.175 mm:
| Inches | Centimeters | Millimeters |
|---|---|---|
| 1 | 2.54 | 25.4 |
| 1 1/8 | 2.8575 | 28.575 |
| 1 1/4 | 3.175 | 31.75 |
| 1 3/8 | 3.4925 | 34.925 |
| 1 1/2 | 3.81 | 38.1 |
| 1 5/8 | 4.1275 | 41.275 |
| 1 3/4 | 4.445 | 44.45 |
| 1 7/8 | 4.7625 | 47.625 |
1 inch in real life
- Rain and snow. 1 in of rain is 25.4 mm. 1 in of fresh snow holds about 0.1 in (2.54 mm) of water at the commonly quoted 10-to-1 ratio, though wet snow holds more and powder less.
Objects of a similar size
- 5% longer than the diameter of a US quarter, 2.43 cm (0.96 in).
- 20% longer than the diameter of a US nickel, 2.12 cm (0.84 in).
- 33% longer than the diameter of a US penny, 1.91 cm (0.75 in).
Inches near 1 in
| Inches | Centimeters | Feet & inches / mm |
|---|---|---|
| 1 in | 2.54 cm | 25.4 mm |
| 2 in | 5.08 cm | 50.8 mm |
| 3 in | 7.62 cm | 76.2 mm |
| 4 in | 10.16 cm | 101.6 mm |
| 5 in | 12.7 cm | 127 mm |
| 6 in | 15.24 cm | 152.4 mm |
Going the other way: 3 cm to inches is 1.18 in.
Frequently asked questions
How many cm is 1 inch?
1 inch is exactly 2.54 cm, because one inch is defined as 2.54 cm.
What is 1 inches in mm?
1 in = 25.4 mm (multiply by 25.4).
What is 1 ½ inches in cm?
1.5 in × 2.54 = 3.81 cm.
Is 1 inches the same as 3 cm?
Not quite: 1 in is 2.54 cm, so 3 cm is 4.6 mm too long — close enough for most everyday measuring.