Here's a comparison of different common framings of 120 and 220 film, along with their exposures per roll.

	6x4.5 cm 16 exposures on 120 film 32 exposures on 220 film
	6x6 cm 12 exposures on 120 film 24 exposures on 220 film
	6x7 cm 10 exposures on 120 film 20 exposures on 220 film
	6x9 cm 8 exposures on 120 film 16 exposures on 220 film
	6x12 cm 6 exposures on 120 film 12 exposures on 220 film