Why the 4x6 Postcard Is Still King (Updated May 2026)
Quick answer: The 4" × 6" postcard is still the smartest default size in 2026, and the reason is postage. USPS charges its lowest postcard rate — $0.61 with a stamp — only on cards up to 4.25" × 6". A 4×6 fits comfortably under that ceiling, so it mails for the cheapest possible rate. Go any bigger and USPS bills you at the higher First-Class letter or Marketing Mail rate. That single rule is why, after years of fancier oversized formats, the humble 4×6 still wins on cost-per-piece for most campaigns.
Last updated: May 2026.
We are a print and direct mail shop in Houston, and we run this math with customers every week. Below is the honest breakdown: why the 4×6 is cheapest to mail, how it compares to 5×7, 6×9, and 6×11, and the specific cases where paying for a bigger card actually pays you back.
Why the 4x6 Is the Cheapest Postcard to Mail
Postage, not printing, is where direct mail budgets live or die. Printing a postcard is cheap; mailing thousands of them is where the real money goes. So the size that unlocks the lowest postage rate wins by default — and that is the 4×6.
Here is the rule that decides everything: the USPS postcard rate applies only to cards up to 4.25" × 6". A 4×6 sits right under that line, so it qualifies for the $0.61 First-Class postcard stamp — the lowest retail rate USPS offers for a mailpiece. The moment your card exceeds 4.25" in height or 6" in length, USPS reclassifies it as a letter and charges the higher First-Class letter or Marketing Mail rate instead.
That is the whole secret. The 4×6 is not cheapest because it is small for the sake of being small — it is cheapest because it is the largest card that still qualifies for the rock-bottom postcard rate.
An eighth of an inch can cost you thousands. A card at 4.3" tall does not get the postcard rate — it pays letter rate. On a 10,000-piece mailing, a few cents per piece in the wrong rate bracket is real money. We confirm your exact postage class before anything goes on press.
4x6 vs 5x7 vs 6x9 vs 6x11: The Real Trade-offs
Bigger cards command more mailbox attention — nobody disputes that. The question is whether the extra postage is worth it. Here is how the common sizes line up:
| Size | Postage class | Approx. postage / piece | Trade-off |
|---|---|---|---|
| 4" × 6" | First-Class postcard rate | $0.61 retail / ~$0.25 bulk | Cheapest to mail; least space for a message |
| 5" × 7" | First-Class letter / Marketing Mail | Higher than 4×6 | More room, more presence; loses the postcard rate |
| 6" × 9" | Letter / Marketing Mail; EDDM-eligible | Higher; ~$0.234–$0.247 via EDDM | Strong mailbox impact; great for saturation drops |
| 6" × 11" | Letter / Marketing Mail; EDDM-eligible | Higher; ~$0.234–$0.247 via EDDM | Maximum impact; highest postage and print cost |
Postage as of May 2026. Bulk and EDDM rates require minimum quantities and presort. Always confirm live pricing on the official USPS postage prices page before committing to a run. For a full head-to-head, see our guide to standard vs. oversized postcards.
Notice the pattern: only the 4×6 gets the postcard rate. The 5×7 is barely larger but it crosses the 4.25" × 6" line, so it pays letter-rate postage. If your only goal is the lowest cost to deliver a message, the 4×6 is mathematically hard to beat.
When a Bigger Card Is Worth the Extra Postage
We are not going to pretend the 4×6 is always the right answer — that would be lazy advice. Sometimes paying more postage for a 6×9 or 6×11 is the smarter move. Here is when:
- You need to stand out in a crowded mailbox. An oversized 6×11 dominates a stack of mail in a way a 4×6 simply cannot. For high-ticket offers (real estate, auto, home services), the extra presence can lift response enough to cover the postage.
- You are running EDDM. Every Door Direct Mail favors larger formats, and 6×9 and 6×11 are top EDDM sizes. Because EDDM postage runs about $0.234–$0.247 per piece regardless, the size penalty largely disappears — so go big. See our full-service EDDM page.
- You have a lot to say. Multiple offers, a coupon, a map, a QR code, and a strong headline all at once need room. Cram them onto a 4×6 and nothing reads.
- The product is visual. Listings, menus, before-and-after photos, and portfolios reward a larger canvas.
The honest rule of thumb: if you are mailing a targeted First-Class or Marketing Mail list and want the most reach per dollar, choose the 4×6. If you are saturating neighborhoods with EDDM or selling something where mailbox impact drives the sale, step up to a 6×9 or 6×11.
How Much Does It Cost to Mail a 4x6 Postcard?
The retail stamp is only one of several ways to mail a 4×6, and it is the most expensive per piece. Your real cost depends on how you send them:
- First-Class postcard stamp — $0.61. Best for small or time-sensitive sends. Fast (1–5 business days) and undeliverable pieces come back to you.
- USPS Marketing Mail (bulk) — about $0.25/piece. Requires 200+ pieces, a permit, and presort — all of which we handle. This is where postcard campaigns get affordable.
- EDDM Retail — about $0.234–$0.247/piece. Blankets entire carrier routes with no mailing list required. Note that EDDM minimum sizes push you toward larger cards.
For the full cost picture — printing, list, processing, and postage as a zero-markup pass-through — see our postage & mailing costs guide. Heads up: USPS has proposed raising the postcard stamp to $0.65 effective July 12, 2026 (pending Postal Regulatory Commission approval), per the official 2026 USPS price change notice. Even after that bump, the 4×6 keeps its rate advantage over larger cards.
Designing a 4x6 That Punches Above Its Size
The one real drawback of the 4×6 is space — you have to be disciplined. The cards that perform follow a few rules:
- One offer, one headline. Do not try to say five things. Lead with the single most compelling reason to act.
- A clear call to action. A phone number, a QR code, or a short URL — tell people exactly what to do next.
- Bold contrast and big type. The card is small; the message should not be. It has to read in the half-second between the mailbox and the recycling bin.
- A trackable code or number. Unique promo codes and call-tracking numbers let you measure response and prove ROI.
Ready to order? Browse stocks, coatings, and finishes on our postcard printing page.
Size & postage — the part to get right: on Standard / Marketing Mail (what most bulk postcard campaigns use), all of these sizes mail as "letters" at the same postage — a 6×9 costs the same to mail as a 4×6. Size only changes postage on First-Class, where only a card up to 4.25" × 6" earns the low postcard rate. On a bulk drop, going bigger for impact usually costs nothing extra; what drives Standard-rate cost is weight and address density.
4x6 Postcard FAQ
What is the cheapest size postcard to mail?
The 4" × 6" postcard. It is the largest card that still fits under the USPS 4.25" × 6" postcard-rate ceiling, so it qualifies for the lowest rate — $0.61 with a stamp in 2026. Larger sizes pay the higher letter or Marketing Mail rate.
Why does a 4x6 postcard cost less to mail than a 5x7?
Because the USPS postcard rate applies only to cards up to 4.25" × 6". A 4×6 qualifies; a 5×7 exceeds the limit and is billed at the First-Class letter or Marketing Mail rate, which is higher.
Is a 4x6 postcard too small for marketing?
Not for most campaigns. With one clear offer, a strong headline, and an obvious call to action, a 4×6 performs well and mails for the lowest cost. Step up to a 6×9 or 6×11 when you need maximum mailbox impact or are running EDDM.
When should I use a 6x9 or 6x11 instead?
When mailbox dominance drives the sale (high-ticket offers), when you have a lot to communicate, or when you are saturating neighborhoods with EDDM — where larger formats are standard and the per-piece postage is roughly the same regardless of size. See our standard vs. oversized guide.
How much is postage for a 4x6 postcard in 2026?
A single First-Class postcard stamp is $0.61 in 2026. In bulk, Marketing Mail runs about $0.25/piece and EDDM about $0.234–$0.247/piece. A proposed increase to $0.65 is pending for July 12, 2026 — always confirm the live rate on USPS.com before printing.
Can I mail a 4x6 postcard with a regular Forever stamp?
You can, but you would be overpaying. A standard Forever (letter) stamp is more than the postcard rate. For a qualifying 4×6, use the cheaper postcard stamp — or let us presort the mailing so you pay the bulk rate instead.
Ready to Mail Your 4x6 Postcards?
Catdi Printing prints and mails 4×6 postcards — and every other common size — right here in Houston, and we estimate your real postage before you commit a dollar. Get a free, itemized direct mail quote with postage included, or call us at (713) 882-4629 and we will help you pick the size that gets the most reach for your budget.