How to print 4x6 shipping labels on a Mac

Getting a shipping label out of a Mac at the right size comes down to two separate questions, and mixing them up is why the problem feels harder than it is.

First: is the PDF the right shape? A file that is already 4x6 is a print-settings problem. Second: are the print settings right? A file that is a full A4 or Letter page with the label in one corner is not — and no print setting fixes it.

Work out which one you have before changing anything, or you will spend an afternoon adjusting settings that were never the cause.

Step 1: check what shape your PDF actually is

Open the file in Preview and press Cmd+I for the inspector. Read the page size.

• 100 × 150 mm or 4 × 6 in — the file is fine. Go to step 2.
• 210 × 297 mm (A4) or 8.5 × 11 in (Letter) — the label is a small rectangle on a big page. Step 2 will not help; go to the guide on labels that print too small, which covers cutting the label out.

Step 2: add a 4x6 paper size

Select your thermal printer first. macOS only offers the paper sizes the current printer reports, so a 4x6 option that is missing often just means a different printer is selected.

1. Open the file, then File → Print, and click Show Details if the dialog is collapsed.
2. Pick the thermal printer from the printer menu.
3. Open Paper Size. If 4 × 6 or 100 × 150 mm is listed, choose it and skip to step 3.
4. Otherwise choose Manage Custom Sizes, click +, and enter 100 mm wide by 150 mm tall.
5. Set all four margins to 0. This is the part people miss.
6. Name it something you will recognise, click OK, and select it.

Non-zero margins are worth repeating because they produce exactly the symptom that sends people looking for a driver problem. macOS treats a margin as unprintable area and scales your label down until it clears it. You get a slightly small label with a white border, on a printer that is working perfectly.

Step 3: turn scaling off

In the same dialog, set Scale to 100%, or untick Scale to Fit if that is what your app offers. Where there is a Margins option, set it to None.

Fit-to-page exists to stop documents being clipped, which is the right default for a contract and the wrong one for a label that is already exactly the size of the paper. It will shave a few percent off every print, which is enough to make small barcode text unreliable at the scanner.

Step 4: set the printer's default so you stop repeating this

macOS remembers a default paper size per printer and falls back to it whenever a document does not specify one — which for a lot of label PDFs is always. If that default is still Letter, every print starts from the wrong assumption.

Open System Settings → Printers & Scanners, select the thermal printer, and set its default paper size to your 4x6. This is the step that turns a working print into a working setup.

Printing from a browser

Avoid it where you can. Browser print paths add their own margins, headers and scaling, and some re-render the PDF rather than passing it through, which softens barcodes.

When you have no choice, open the system print dialog rather than the browser's own preview, set scale to 100%, paper size to 4x6, margins to none, and turn headers and footers off.

When the settings are right and it still comes out wrong

At that point it is nearly always the file rather than the printer. The usual culprits:

• The label is on an A4 page. Covered above — the page has to be cut down first.
• The page arrives rotated. The PDF carries a rotation flag and the printer honours it, so the label comes out sideways on the roll.
• Several labels share one sheet. Printing that as one page gives you four tiny labels on one 4x6.

All three are fixable by hand once. The problem is that they are fixable by hand every single time, because the next order produces the same file from the same source.

If your file is a full page rather than a label, our free browser tool crops it down before you print — it finds the label, keeps it at full size, and runs entirely in your browser.