Most people guess low. Here's the math.
The baseline
A healthy dog produces waste at roughly 2-3% of its body weight per day.
Volume and bin capacity
A pound is roughly the size of a softball. Two 50-pound dogs = roughly two gallons of waste per week.
Diet effects
Higher-quality kibble = less waste. Cheap fillers = more waste. Raw-fed dog waste breaks down faster but smells stronger short-term.
Why the number matters
If you have two 60-lb Labs producing 14 piles a week, twice-weekly service starts making sense.