Kilobytes to gigabytes (kB to GB)

One kilobyte is exactly 0.000001 gigabytes: a kilobyte is 1,000 bytes and a gigabyte 1,000,000,000, by the SI prefixes. The factor is a definition provided both ends are decimal, and that proviso is the whole question with this pair.

Worked through: 10,000 kB x 0.000001 = 0.01 GB.

Going the other way, one gigabyte is 1,000,000 kilobytes.

For mental arithmetic: Move the decimal point six places left. 500,000 kB is 0.5 GB.

A million kilobytes to the gigabyte, if both are decimal. The trouble is that KB is the least standardized prefix in computing: the SI symbol is lower-case kB for 1,000 bytes, while a capital-K KB was used for decades to mean 1,024, and older software, some file managers and many spec sheets still use it that way. In binary units a gibibyte is 1,048,576 kibibytes, so a figure converted in the wrong base is out by about 4.9% at this scale. Email attachment limits, upload caps and log sizes are the usual places these two meet, and the safe reading of any limit is the smaller of the two.

Precision is worth matching to the input. A measurement given as 100 kB carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.