3 mm to km — 3 millimetres in kilometres
Exact 3 ÷ 1,000,000 = 0.000003
3 millimetres in other units
| Nanometres | 3,000,000 | nm |
|---|---|---|
| Micrometres | 3,000 | µm |
| Centimetres | 0.3 | cm |
| Metres | 0.003 | m |
| Kilometres | 0.000003 | km |
| Inches | 0.11811024 | in |
| Feet | 0.009842519685 | ft |
| Yards | 0.003280839895 | yd |
| Miles | 0.000001864114 | mi |
| Nautical miles | 0.00000161987 | nmi |
mm to km at a glance
| Millimetres | Kilometres |
|---|---|
| 1 mm | 0.000001 km |
| 2 mm | 0.000002 km |
| 3 mm | 0.000003 km |
| 5 mm | 0.000005 km |
| 10 mm | 0.00001 km |
| 20 mm | 0.00002 km |
| 25 mm | 0.000025 km |
| 50 mm | 0.00005 km |
| 100 mm | 0.0001 km |
| 250 mm | 0.00025 km |
| 500 mm | 0.0005 km |
| 1,000 mm | 0.001 km |
How to convert millimetres to kilometres
Multiply by 0.000001 — one millimetre is 0.000001 kilometres. That factor is exact: it comes from the definition of the units rather than from a measurement, so it will not change and does not need rounding.
Working 3 ÷ 1,000,000 = 0.000003
What these units are
The millimetre and the kilometre are covered in the length unit guide, along with every other unit on this page.
Questions
How many kilometres are in a millimetre?
One millimetre is 0.000001 kilometres. This figure is exact — it comes from the definition of the unit, not a measurement.
What is 3 millimetres in kilometres?
3 millimetres is 0.000003 kilometres. The working is 3 ÷ 1,000,000 = 0.000003.
Is an inch exactly 2.54 centimetres?
Yes, exactly. Since 1959 the international inch has been defined as 25.4 millimetres, so the figure is a definition rather than a measurement. Every foot, yard and mile figure on this page follows from it and is equally exact.
Why is a nautical mile different from a mile?
It is tied to the Earth rather than to a body part. One nautical mile is one minute of latitude, fixed at exactly 1,852 metres, which makes chart work straightforward for anyone navigating by degrees.
How do I write my height in metric?
Convert the whole thing to inches first, then multiply by 2.54. Five foot ten is 70 inches, which is 177.8 cm. Converting the feet and the inches separately is where the arithmetic usually goes wrong.
Meter or metre?
Both name the same unit. "Metre" is the international spelling used by the SI and most English-speaking countries; "meter" is standard in the United States. Either spelling will find this page.