What is 9mm f5 6 on aps c in full frame?

9mm on APS-C gives the view of 14mm on full frame. For the same depth of field, f/5.6 there behaves like about f/8.4 on full frame. Exposure doesn't change: f/5.6 gives the same brightness on any sensor.

The same view on every common format:

• Medium format (44 x 33): 17mm at about f/10.6 for the same depth of field
• Full frame: 14mm at about f/8.4 for the same depth of field
• APS-C (yours): 9mm at about f/5.6 for the same depth of field
• APS-C (Canon): 8.4mm at about f/5.2 for the same depth of field
• Micro Four Thirds: 6.8mm at about f/4.2 for the same depth of field
• 1-inch: 5mm at about f/3.1 for the same depth of field
• 1/1.3-inch: 3.7mm at about f/2.3 for the same depth of field
• 1/1.7-inch: 2.9mm at about f/1.8 for the same depth of field
• 1/2.3-inch: 2.4mm at about f/1.5 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.