Question: what size are 6d nails?
Answer: 4d nails measure 1.5 inches and 5d nails measure 1.75. A 6d nail is 2 inches long and an 8d nail is 2.5 inches long. 12d nails are 3.25 inches long and 16d nails (16 penny) are 3.5 inches long. The nail size chart below shows how they stack up against each other.