According to Integra Information Systems industry profiles, general line grocery merchant wholesalers make a gross margin of 13.11 percent on average--so they have a markup of 15 percent. Those are wholesalers, also called distributors, who buy in volume and sell to retailers. A gross margin of 13.11 percent means what they buy for $86.89 they sell for $100, so the markup is calculated by dividing $13.11 by $86.89.
Grocery stores in general have even smaller markup. Their gross margin is 10.47 percent on average, so their markup is 12 percent.
The data comes from inside Business Plan Pro (http://www.paloalto.com/business_plan_software), in industry research reports sourced from Integra Information Systems.