Postcard design specs: bleed, DPI, and safe zones without the jargon
Print has three rules screens never taught you: resolution, bleed, and safe zones. Miss them and a design that looked perfect on a monitor comes back soft, white-edged, or with text under a postage barcode. Here is each one in plain English, plus the exact numbers for a standard 4×6 postcard.
Resolution: why 300 DPI
Screens forgive because they glow; paper doesn’t. Print needs about 300 dots per inch to look sharp at reading distance. For a 4×6 card (which actually prints at 6.25×4.25 inches — see bleed below) that means artwork of 1875×1275 pixels. Below roughly 180 DPI, edges go fuzzy in a way everyone notices even if nobody names it.
| Artwork size | Effective DPI | Verdict |
|---|---|---|
| 1875 × 1275 px | 300 | Crisp — the target |
| 1400 × 950 px | ~225 | Usable; fine text may soften |
| 1125 × 765 px | ~180 | The floor — photos only |
| Below that | <180 | Don’t print it |
Bleed: design bigger than the card
Cards are printed on larger sheets and cut down, and the cut drifts a fraction of a millimeter each way. Bleed is the answer: extend your background 0.125″ past the final trim on every side. That’s why a “4×6” card wants 6.25×4.25-inch artwork — the outer eighth-inch ring gets trimmed away, taking the cutter’s drift with it.
Safe zones: keep what matters away from the edge
The same drift that eats bleed can eat content near the trim. Keep text, logos and anything you’d miss at least 0.125″ inside the final edge. And the back has a bigger reservation: USPS requires a clear area for the recipient address, postage and routing barcode — roughly the right half of the back. Ink there and the card may be delayed or rejected. The practical pattern: pour your creativity into the front; keep the back functional (a short message, your return address, a QR) and let your mailing tool own the address layout.
The pre-flight checklist
- Front artwork 1875×1275 px (or a print-exported PDF), backgrounds running to the artwork edge.
- Text and logos ≥ 0.125″ inside the trim; nothing important in the outer ring.
- Landscape orientation for a 4×6 — portrait uploads usually mean a rotated design.
- Back: address zone untouched; QR present so responses are countable.
- Colors: expect print to run slightly darker and less saturated than your screen; very dark, moody designs deserve a test card first.
A good mail tool enforces the floor for you — rejecting artwork too small to print sharply beats mailing 300 blurry cards and refunding nobody’s disappointment. From here, the next question is what to put on the card: postcard campaigns, start to send.
Common questions
›My image is 1200×800 — will it print okay?
It will print, but soft — that is roughly 190 DPI over a 6.25×4.25-inch card. Acceptable for a photo background, risky for fine text or logos. 1875×1275 pixels is the size where everything prints crisp.
›Can I design the back of the card myself?
You can, but the address area is non-negotiable: USPS processing needs a clear zone for the recipient address, postage and barcode. The safest pattern is designing the front freely and letting your mail tool generate a compliant back.
›PDF, PNG or JPG — which should I upload?
A flattened PDF exported for print is the gold standard (it preserves vector text). A PNG or high-quality JPG at 1875×1275 is equally fine for photo-led designs. Avoid anything exported "for web" — it is usually 72 DPI.
›Why did my edge-to-edge color end with a white sliver?
No bleed. The cutter drifts a hair on every card, and artwork sized exactly to the trim line leaves white flashes where it drifts outward. Extend the background past the trim on all sides and the sliver disappears.