Which EDDM postcard size gets the best response rate?

Larger EDDM formats tend to pull the best response rates simply because they are harder to ignore in a mailbox. That said, the best size for you balances response against cost per piece.

• 8.5" x 11" and similar large formats command the most attention and often lift response.
• 6.25" x 9" offers the strongest balance of cost and performance for most small businesses.
• First-time campaigns usually do well starting mid-range, then scaling the winner.

If the goal is a first EDDM test on a budget, the mid-size format is the sensible starting point. Step up to the larger format once you know the offer converts.