CM to KM Converter
A kilometre is exactly 100,000 centimetres, so centimetres to kilometres is one division: km = cm / 100,000. In decimal that is the point moving five places to the left, which is why 1 cm is 0.00001 km, 100 cm is 0.001 km, 10,000 cm is 0.1 km and 100,000 cm is 1 km. Both units are defined from the metre, a centimetre as a hundredth of it and a kilometre as a thousand of them, so the ratio is exact rather than measured. Displayed answers round to twelve significant digits, and results smaller than a millionth of a kilometre switch to exponential notation, so 0.1 cm reads 0.000001 while 0.05 cm reads 5e-7. This page opens the converter with Centimetre in the From box and Kilometre in the To box, whatever pair you converted last, and lists the same distance in millimetres, metres, inches, feet, yards, miles and nautical miles under the answer.
1 cm in every length unit
Common questions
- How many km is 1 cm?
- 0.00001 km, because one hundred thousand centimetres make one kilometre. The pattern holds at every size: 5 cm is 0.00005 km, 50 cm is 0.0005 km, 250 cm is 0.0025 km, 1,000 cm is 0.01 km and 10,000 cm is 0.1 km. The conversion moves the decimal point five places to the left; the displayed result may round longer inputs to twelve significant digits.
- What is the formula for cm to km?
- Kilometres = centimetres / 100,000, and centimetres = kilometres × 100,000 in the other direction. Centi means a hundredth of a metre and kilo means a thousand metres, so the gap between the two prefixes is 10 × 1,000, which is 100,000 exactly. Nothing in that number is an approximation, so 500,000 cm comes back as 5 with nothing trailing after the decimal point.
- How many centimetres are in a kilometre?
- Exactly 100,000. Half a kilometre is 50,000 cm, 0.4 km is 40,000 cm and 1.5 km is 150,000 cm. A statute mile is 1,609.344 m by definition, which is 160,934.4 cm, and the converter reads that back as 1.609344 km.
- Can I convert kilometres back to centimetres on this page?
- Yes. Press the Swap units button between the two boxes and the pair reverses without a reload: type 1 and the answer is 100,000 cm, and 0.4 km reads as 40,000 cm. Both unit menus stay open too, so the same number will go from centimetres to millimetres, metres, inches, feet or miles without leaving the page.
- Does dividing by 100,000 also work for square centimetres?
- No, and this is where the mistake usually happens. Area squares the ratio, so one square kilometre is 100,000² square centimetres, which is 10,000,000,000 cm², and one square centimetre is 0.0000000001 km². Use the Area category chip above the converter for that: square centimetres and square kilometres are both in its list, along with square metres, hectares, acres, square feet and square miles.
- Why does the page open on cm and km when I last converted something else?
- Because a page that names a pair should show that pair. This one sets centimetres and kilometres on arrival, ahead of whatever the converter last remembered, and it leaves the main unit converter's own memory alone: go back there and it is still on the pair you left it on. The number you last typed does come with you, since it is usually the one you are still working on.
- How precise is the answer, and can I copy it?
- The conversion is a single division by 100,000 carried out in double precision, and the headline prints to twelve significant digits with trailing zeros dropped, so 100,000 cm reads as 1 rather than 1.00000000000. Twelve digits sits well inside what the arithmetic carries, and it absorbs the floating-point residue that appears in units that do not divide evenly: 100 cm in the Mile row reads 0.000621371192237. Copy result puts the headline on the clipboard exactly as printed, without the thousands separators.
- What is the same distance in metres, feet or miles?
- The list under the answer already has it, because the converter works out every common length unit at once rather than one target at a time. Type 100 in the From box and it reads 0.001 km in the headline, 1 m for metres, 1,000 mm for millimetres, 39.3700787402 in for inches, 3.28083989501 ft for feet and 1.09361329834 yd for yards. Seven rarer length units, including micrometres, furlongs, light years and parsecs, sit behind the Show 7 more switch in the readout.
Conversion factors are the exact legal definitions where one exists. An inch is exactly 2.54 cm and a pound exactly 0.45359237 kg, so those conversions are exact rather than approximate. Temperature uses offsets rather than factors, and that is shown in the working.