Convert kilometres to millimetres

One kilometre is 1000000 millimetres. To convert any amount, multiply by 1000000. Going the other way, one millimetre is 0.000001 kilometres.

Multiply the kilometre figure by 1000000. So mm = km × 1000000. For a quick mental estimate, multiplying by about 1000000 gets you within a percent or so, which is close enough for most everyday purposes.

One kilometre is about a 12-minute walk. The kilometre is the standard road-distance unit everywhere except the United States, the United Kingdom and a handful of small territories.

One millimetre is roughly the thickness of a credit card, which is 0.76 mm. The millimetre is the working unit of engineering drawings and machining tolerances almost everywhere metric is used, because it avoids decimals for most part dimensions.

Yes. Since the 1959 international yard and pound agreement, the imperial and metric systems are related by exact definitions rather than measurements — the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg. Everything derived from those, including this conversion, is therefore exact. Round at the end rather than partway through, since rounding km before converting introduces an error the conversion then multiplies.