What is 45mm on micro four thirds in full frame?

45mm on Micro Four Thirds gives the view of 90mm on full frame.

The same view on every common format:

• Medium format (44 x 33): 114mm
• Full frame: 90mm
• APS-C: 60mm
• APS-C (Canon): 56mm
• Micro Four Thirds (yours): 45mm
• 1-inch: 33mm
• 1/1.3-inch: 25mm
• 1/1.7-inch: 20mm
• 1/2.3-inch: 16mm

Crop factors are by the sensor diagonal, rounded as they're usually quoted; a format with a different shape (4:3 against 3:2) frames a little differently across the width. More in the focal length converter.

Computed from the sensor sizes, not written by a model.