It would be impossible to tell really. I've seen puffy nugs that look like way more than they should be. I've seen compact bud that looks like it's half of what it should be. Also moisture contents... lol just get a scale man. Hell even a cheapo key chain scale will tell ya if it's close or not.
Oh also midgrades and brick weed to some good dank... big diffrence. You can fit like 5 ounces of brick weed in an ounce of dank.