3 inches in cm
3 in = 7.62 cm = 76.2 mm = 0.0762 m
Working: 3 × 2.54 = 7.62
3 inches is 7.62 centimetres, or 76.2 millimetres.
The conversion is exact rather than approximate: since 1959 the international inch has been defined as precisely 2.54 centimetres, so multiplying by 2.54 gives an exact answer with no rounding error. 3 × 2.54 = 7.62 cm. To go back the other way, divide by 2.54; for millimetres, multiply the inches by 25.4 instead.
Metric trades work in millimetres rather than centimetres, and 3 inches is 76.2 mm — the figure a drawing or a parts list would actually carry. The nearest whole centimetre is 8, 0.38 cm away.
Three inches is the standard diameter for a great deal of plumbing and ducting in North America, where pipe is sized in nominal inches. The metric equivalent is 76.2 mm, and European systems use 75 mm — close enough to look compatible and different enough that adapters exist.
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Frequently asked questions
How many cm is 3 inches?
3 inches is 7.62 cm. Multiply the number of inches by 2.54 to convert to centimetres.
Is the inch to cm conversion exact?
Yes. The international inch has been defined as exactly 2.54 centimetres since 1959, so the conversion introduces no rounding error.
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