The focal length of a lens determines the magnification at which it images distant objects. It is measured in mm and classifies lenses. But it is not absolute value across the formats. If the sensor or film is smaller, more magnification is present with the same lens. Therefore only absolute value for comparing lenses between different formats is angle of view.  Crop factor is a value that determines relation between the focal length on different formats.

4/3 has crop factor 2 compared to Full Frame 35mm(FF35). That means the same lens used on M4/3 will look twice longer than on FF35. Here is comparison of focal length on different formats.

If you want to check how will FF35 lens look on your 4/3 camera – find it in the 4/3 column and slide to FF35 column to see your FF35 equivalent .

If you want to find out what length do you need on 4/3 to have same angle as your FF35 lens – find it in FF35 column and slide to 4/3 column.

Conclusion – You need 1/2 of the focal length on 4/3 camera to get the same picture as on FF35.