Set of tables that give a quick guide to the 35mm equivalent in various medium format frame sizes.

645 Crop Factor = 0.62

645 LENS35MM LENS EQUIVALENT
45mm28mm
55mm34mm
60mm37mm
80mm50mm
100mm62mm
120mm75mm
150mm93mm
200mm124mm

6×6 Crop Factor = 0.55

6×6 LENS35MM LENS EQUIVALENT
40mm22mm
50mm28mm
60mm33mm
80mm44mm
120mm66mm
150mm83mm
180mm99mm
200mm110mm

6×7 Crop Factor = 0.5

6×7 LENS35MM LENS EQUIVALENT
45mm23mm
50mm25mm
65mm33mm
90mm45mm
105mm53mm
180mm90mm
200mm100mm
250mm125mm

6×9 Crop Factor = 0.43

6×9 LENS35MM LENS EQUIVALENT
65mm28mm
90mm39mm
100mm43mm
105mm45mm
150mm65mm

Hope that is useful to you.