What is 45mm f1 8 on micro four thirds in full frame?

45mm on Micro Four Thirds gives the view of 90mm on full frame. For the same depth of field, f/1.8 there behaves like about f/3.6 on full frame. Exposure doesn't change: f/1.8 gives the same brightness on any sensor.

The same view on every common format:

• Medium format (44 x 33): 114mm at about f/4.6 for the same depth of field
• Full frame: 90mm at about f/3.6 for the same depth of field
• APS-C: 60mm at about f/2.4 for the same depth of field
• APS-C (Canon): 56mm at about f/2.2 for the same depth of field
• Micro Four Thirds (yours): 45mm at about f/1.8 for the same depth of field
• 1-inch: 33mm at about f/1.3 for the same depth of field
• 1/1.3-inch: 25mm at about f/1 for the same depth of field
• 1/1.7-inch: 20mm at about f/0.8 for the same depth of field
• 1/2.3-inch: 16mm at about f/0.6 for the same depth of field

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.