Yes we are 100% sure. We measured before we ever got the fence, then after we bought the fence, then before we even installed it we blocked him with it in the house and called for him to see if he could squeeze though, despite his best efforts he was unable to. Also as I already stated he will not be unattended, and in the event of a freak accident and he does somehow manage to escape he will still be behind another fence. I promise everyone our dog is 100% safe.