We usually calculate flyers by the thousands, 1k, 2k ,3k and so on...
Based on many campaigns, on a general basis (as many factors are involved) the range of response from flyers are usually between 1% to 4%.
Most businesses campaigns from others I know generate between 1% to 2% of response.
1000 flyers, 1% is 10 leads
1000 flyers, 4% is 40 leads
2000 flyers, 1% is 20 leads
2000 flyers, 4% is 80 leads
The percentage may look small but if you have a product that have a good enough profit margin, it will more than cover for it.
Hope these numbers help in your calculations and planning if you intend to give out flyers
There is an art to creating flyers that convert well near the 4% mark but that's another story for another day