Check out the following land usage statistics for Prospect Park. I will eventually post the same for all parks with designated off-leash privileges:
Prospect Park Total area: 526.25 acres
Open Spaces in Prospect Park
Rose Garden: ~1 acre
Nelly's Lawn: ~3 acres
Peninsula Meadow: ~ 3 acres
Nethermead Meadow: ~15 acres
Long Meadow: 90 acres
Total open space (field or meadow): 112 acres
Designated Off-leash Areas
Long Meadow: 90 acres
Nethermead Meadow: ~15 acres
Peninsula Meadow: ~ 3 acres
Total open space designated as off-leash: 108 acres
Total terra firma in Prospect Park (open spaces + wooded habitats)
Prospect Lake: 60 acres
Land mass minus Prospect Lake: 526.25 - 60 = 466.25
Total percentage of Prospect Park's terra firma designated as off-leash areas: 26.16%
Total open space (field or meadow): 112 acres
Total "official" off-leash areas: 108 acres
Total percentage of open spaces designated as off-leash areas: 96.4%
These numbers are pointless, however, because the policy is not enforced anywhere in the park.