Amazon FBA Label Printing: Sizes, Settings and Splitting

Rejected FBA shipments over unreadable labels are the most avoidable problem in the whole fulfilment process. The barcode Amazon generates is always fine — what goes wrong happens between Seller Central and the sticker on the box. This guide covers the parts you control: label size, how to get single labels out of an A4 grid, and the printer settings that decide whether a scanner reads your FNSKU first time.

What the FNSKU label actually is

Every product you send to an Amazon fulfilment centre needs its own barcode so the warehouse can tell your unit apart from every other seller's. That is the FNSKU — a code beginning with X00 or B0, printed as a Code 128 barcode with the product name and condition underneath.

Seller Central gives you these labels as a PDF grid: typically 24 labels on an A4 sheet in a 3 × 8 layout, sometimes 40-up, occasionally other arrangements depending on the label size you picked. That grid is designed for A4 sticker paper fed through a laser printer.

Label sizes

Amazon publishes an accepted size range for FNSKU labels, and the common choices in India are 50 × 25 mm thermal stickers or the 24-up and 40-up A4 sheets. The exact accepted range does change from time to time, so confirm the current minimum and maximum in Seller Central rather than trusting any third-party page — including this one.

What does not change is the requirement that the barcode be scannable, undamaged, and not wrapped around a corner or covered by tape. Size only matters insofar as it serves that.

Splitting an A4 grid into single labels

If you have moved to a thermal printer, the A4 grid is useless as it stands: a thermal printer wants one label per page, at the size of the roll. Sheets are also wasteful when a shipment needs eleven labels and the sheet holds twenty-four.

The Amazon FBA Label Splitter turns the grid into single labels. It measures the white gutters between labels on the fullest page in your file, works out the row and column positions from those gaps, and applies the same grid to every page. Blank cells on part-used sheets are skipped, so a half-empty sheet produces only the labels that exist rather than a run of empty pages.

Two details are worth knowing. The cut is vector-based, meaning the barcode is copied rather than re-photographed — a split label prints exactly as sharp as the original sheet. And if a sheet has an unusual layout, you can untick auto detection and type the rows and columns yourself; the preview updates immediately so you can confirm the orange grid lines fall in the gutters rather than through a label.

If your file mixes several products, Split by product reads the ASIN or FNSKU printed on each label and gives you one PDF per product. The button shows the code it found before you press it, so you can confirm it read the right thing.

Fitting labels to your sticker size

Printing on 50 × 25 mm stock? Open More options → Fit to label stock and enter the size in millimetres. Each label is trimmed to its ink, centred on the page, and given a quiet zone — a margin of white around the barcode — so the bars never touch the sticker edge. A barcode with no quiet zone is one of the quieter causes of scan failures, because the scanner cannot tell where the code begins.

The same option handles other common sizes: 100 × 150 mm for shipping labels, 38 × 25 mm for small item labels, or anything else your roll happens to be.

Printer settings that keep barcodes scannable

A barcode stores its data in the ratio between bar and space widths. Anything that changes those ratios unevenly damages the code, even when it still looks like a barcode to your eye. That single fact explains almost every setting below.

• Print at 100% or Actual size. Never "Fit to page", "Shrink oversized pages" or "Fit to printable area". This is the number one cause of unscannable labels.
• Set the paper size to the label size, not A4, when using a thermal printer. Margins to none.
• Use a laser or thermal printer. Inkjet ink bleeds into paper fibres and thickens the bars.
• Check your PDF viewer as well as the driver. Some viewers apply their own scaling on top of the printer's settings, and the two combine.
• Keep thermal darkness in the middle. Too light gives grey bars; too dark bleeds them together. If your labels look washed out, the roll may also be the wrong side up or a low-grade thermal stock.
• Do not photocopy labels. Every generation of copying degrades edge sharpness.

Applying labels to units

Place the label on a flat face, not over a seam, edge or curve. Do not cover it with tape — even clear tape can create glare that defeats a laser scanner. If the product's own packaging carries a manufacturer barcode, cover that one completely, or the warehouse may scan the wrong code. On polybags, apply the label to the flat side after the bag is sealed, not while it is loose.

A 30-second check before a big run

Print one label. Scan it with any free barcode app on your phone. If your phone reads the FNSKU, a warehouse scanner — which is far more capable than a phone camera — will read it too. Then check the printed size with a ruler against what you intended; a mismatch there tells you scaling is still on somewhere in the chain.

Do this once when you set up a new printer or roll, and then only when something changes. It costs one sticker and prevents the kind of problem you discover three weeks later as an unfulfillable-inventory notice.

Common problems

The grid detected the wrong number of rows or columns. Turn off auto detection and enter the numbers manually; the preview confirms it instantly.

Split by product is disabled. The sheet has no selectable text, so no ASIN can be read. Splitting still works — only grouping needs text.

Labels print slightly smaller than expected. Your print dialog is scaling. Set it to 100% and print again.

The barcode scans on screen but not on paper. Print quality, not the file. Check printer type, darkness and whether anything is scaling the page.

Once the setup is right it stays right, and label printing stops being something you think about. If you also ship your own orders rather than through FBA, the Amazon Easy Ship Label Cropper handles those pages, where the shipping label and tax invoice share a sheet.