All exported data has units of meters, so in your 3D viewer or editing tool one unit = 1 meter by default.
However, some 3D editors adjust the scale of data when they import it, so you will need to refer to the import protocol for your specific program if it doesn't seem like 1 meter = 1 unit for you.
For example, for 3DS Max we have heard that you need to apply a uniform scaling up by a factor of 3800 to achieve a 1 unit = 1 meter ratio.