centimetre
An SI unit of length equal to 10⁻² metres. Symbol: cm
centimetre: one hundredth of a metre, the workhorse of the shop floor
A centimetre is 0.01 metres, or 10 millimetres. It occupies the practical middle ground between the metre (too coarse for most component work) and the millimetre (often unnecessarily precise). On machine tools, bench scales, and measuring tapes, the centimetre is the first subdivision you see; it sits naturally between human scale and industrial tolerance.
In everyday manufacturing, centimetres appear most often in rough-in work: the initial placement of stock before machining, the spacing of bolt holes on a bracket, the height of a workpiece in a vise. Many shop rulers and height gauges divide their major graduations in centimetres. Hand-drawn sketches and quick layout work commonly reference centimetres because they are easy to estimate and verify by eye.
Where the centimetre reaches its limit
For precision work, the centimetre is too coarse. A tolerance of plus or minus 0.5 cm (plus or minus 5 mm) is loose by any serious standard. Once dimensions enter the realm of fits, bores, or surface finishes, metrologists and machinists drop to millimetres or micrometres. Blueprints for finished parts rarely specify dimensions in centimetres alone; when they do, it signals a non-critical or reference dimension.
The centimetre persists in construction, carpentry, and rough fabrication partly because of habit and partly because it matches the scale at which humans naturally judge distances. In metalworking inspection, however, it is rarely the unit of record. Digital calipers, micrometres, and dial indicators report in millimetres or smaller units. A centimetre on a tape measure is useful for confirming that a subassembly is in the ballpark; it is useless for verifying a press fit or a critical assembly height.
The SI symbol cm is universal, but you will hear the term pronounced differently across regions and trades. In the context of dimensioning or specification, always verify whether a drawing written in centimetres is in fact what was intended, or whether millimetres were meant. A slip of one decimal place can lead to parts that do not fit.