What is 20 35mm on medium format in full frame?

20-35mm on medium format gives the view of 16-28mm on full frame.

The same view on every common format:

• Medium format (44 x 33) (yours): 20-35mm
• Full frame: 16-28mm
• APS-C: 11-18mm
• APS-C (Canon): 9.9-17mm
• Micro Four Thirds: 7.9-14mm
• 1-inch: 5.9-10mm
• 1/1.3-inch: 4.4-7.7mm
• 1/1.7-inch: 3.4-6mm
• 1/2.3-inch: 2.8-4.9mm

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.