What is 90mm f2 2 on aps c in full frame?

90mm on APS-C gives the view of 135mm on full frame. For the same depth of field, f/2.2 there behaves like about f/3.3 on full frame. Exposure doesn't change: f/2.2 gives the same brightness on any sensor.

The same view on every common format:

• Medium format (44 x 33): 171mm at about f/4.2 for the same depth of field
• Full frame: 135mm at about f/3.3 for the same depth of field
• APS-C (yours): 90mm at about f/2.2 for the same depth of field
• APS-C (Canon): 84mm at about f/2.1 for the same depth of field
• Micro Four Thirds: 68mm at about f/1.7 for the same depth of field
• 1-inch: 50mm at about f/1.2 for the same depth of field
• 1/1.3-inch: 38mm at about f/0.9 for the same depth of field
• 1/1.7-inch: 29mm at about f/0.7 for the same depth of field
• 1/2.3-inch: 24mm 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.