What is 10 20mm on canon aps c in full frame?

10-20mm on APS-C (Canon) gives the view of 16-32mm on full frame.

The same view on every common format:

• Medium format (44 x 33): 20-41mm
• Full frame: 16-32mm
• APS-C: 11-21mm
• APS-C (Canon) (yours): 10-20mm
• Micro Four Thirds: 8-16mm
• 1-inch: 5.9-12mm
• 1/1.3-inch: 4.4-8.9mm
• 1/1.7-inch: 3.5-7mm
• 1/2.3-inch: 2.9-5.7mm

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.