Pond size should be driven by what you want to use it for and what your property can reasonably support — not by picking a round number.
Quarter-acre ponds
A quarter acre is a common size for a primarily decorative or small recreational pond, or for properties with limited space or watershed to feed a larger pond. It's the most affordable entry point into pond ownership.
Half-acre ponds
A half acre gives more room for fish stocking and a more substantial water feature, while still being manageable in terms of excavation and dirt placement for most properties.
One-acre and larger ponds
A full acre or more supports serious fishing management, livestock water for larger herds, and a more significant property feature — but requires more watershed to keep it full, more excavated material to deal with, and generally more planning around dam and spillway design.
The right size depends on your watershed (how much natural drainage feeds the pond), how you plan to use it, and your budget. We'll walk through this during a site visit rather than picking a size over the phone.