What is 13 33mm on aps c in full frame?

13-33mm on APS-C gives the view of 20-50mm on full frame.

The same view on every common format:

• Medium format (44 x 33): 25-63mm
• Full frame: 20-50mm
• APS-C (yours): 13-33mm
• APS-C (Canon): 12-31mm
• Micro Four Thirds: 9.8-25mm
• 1-inch: 7.2-18mm
• 1/1.3-inch: 5.4-14mm
• 1/1.7-inch: 4.2-11mm
• 1/2.3-inch: 3.5-8.8mm

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.