Centimetres to inches
Enter a measurement in centimetres to get inches. US carrier size limits are published in inches, so this is the conversion you need to check a metric-measured box against them.
Type a measurement in centimetres and the conversion appears here.
Checking a metric box against US limits
USPS, UPS, and FedEx publish their domestic size limits in inches: 108 in of length, 165 in of length plus girth, and so on. If you measured in centimetres, those numbers mean nothing until they are converted. A 120 cm box is 47.24 in, comfortably inside a 108 in length cap — but 120 cm of length plus girth is a different calculation entirely.
The conversion
Divide centimetres by 2.54, because one inch is defined as exactly 2.54 cm. The division is exact in the sense that nothing is approximated; the decimal simply does not always terminate.
- 2.54 cm = 1 in
- 30.48 cm = 12 in
- 100 cm = 39.37 in
Quick reference
| Centimetres | Inches |
|---|---|
| 1 cm | 0.39 in |
| 5 cm | 1.97 in |
| 10 cm | 3.94 in |
| 20 cm | 7.87 in |
| 30 cm | 11.81 in |
| 40 cm | 15.75 in |
| 50 cm | 19.69 in |
| 60 cm | 23.62 in |
| 100 cm | 39.37 in |
| 165 cm | 64.96 in |
Edge cases worth knowing
- Round down carefully near a limit. A box at 274 cm converts to 107.87 in, just inside a 108 in cap. That is close enough that a carrier's own measurement could put you over.
- Length plus girth must be converted as a whole. Convert each dimension first, then compute length plus girth — or compute it in centimetres and convert the single total. Both work; mixing units halfway does not.
- Millimetres are a common slip. A 300 mm box is 30 cm, not 300 cm. Check which unit the tape was reading.
Common questions
- How many inches is 100 cm?
- 39.37 in, to two decimals.
- Why is the conversion not a round number?
- Because the inch is defined in terms of the centimetre rather than the other way round. 2.54 cm to an inch is exact; the reverse just does not land on a neat decimal.
- Which measurement do carriers actually use?
- For US domestic shipping, inches. Convert first, then compare, and check the result against the girth calculator if you are near a cap.
- Should I round up or down?
- When checking against a maximum, round up. It is the cautious direction, and carriers measure the package themselves.