# ZPL at 203 dpi vs 300 dpi

Source: https://openzpl.com/guides/zpl-203-vs-300-dpi/ (updated 2026-10-20)

ZPL coordinates are in dots, so the same ZPL prints about a third smaller on a 300 dpi printer than on a 203 dpi one: 12 dots per millimetre instead of 8. Either rewrite the coordinates for the new density or add ^MUD,200,300 at the start of the label to scale them.

## Same ZPL, two printers

The box below is 560 dots wide in both renders. At 203 dpi that is 70 mm; at 300 dpi it is 46.7 mm, because each dot is smaller. The label is 4 × 2 in in both.

8 dpmm (203 dpi):
```zpl
^XA
^FO20,20^GB560,200,4^FS
^FO40,50^A0N,50,50^FDSame ZPL^FS
^FO40,120^A0N,30,30^FD560 x 200 dots box^FS
^XZ
```

12 dpmm (300 dpi):
```zpl
^XA
^FO20,20^GB560,200,4^FS
^FO40,50^A0N,50,50^FDSame ZPL^FS
^FO40,120^A0N,30,30^FD560 x 200 dots box^FS
^XZ
```

## Exact densities

Printers are named by rounded dpi, but they are built in dots per millimetre (dpmm), and the OpenZPL API, like Labelary's, takes dpmm. The exact dpi is dpmm × 25.4:

| Printer sold as | dpmm | Exact dpi | One dot |
|---|---|---|---|
| 152 dpi | 6 | 152.4 | 0.167 mm |
| 203 dpi | 8 | 203.2 | 0.125 mm |
| 300 dpi | 12 | 304.8 | 0.083 mm |
| 600 dpi | 24 | 609.6 | 0.042 mm |

So "300 dpi" is really 304.8. Computing dots with 300 instead of 304.8 drifts by 1.6%: 29 dots across a 6 in label.

## Label sizes in dots

Dots = millimetres × dpmm, from the exact density. ^PW and ^LL take whole dots, so round down:

| Label | 6 dpmm | 8 dpmm | 12 dpmm | 24 dpmm |
|---|---|---|---|---|
| 4 × 6 in (101.6 × 152.4 mm) | 609 × 914 | 812 × 1219 | 1219 × 1828 | 2438 × 3657 |
| 4 × 2 in (101.6 × 50.8 mm) | 609 × 304 | 812 × 406 | 1219 × 609 | 2438 × 1219 |
| 2 × 1 in (50.8 × 25.4 mm) | 304 × 152 | 406 × 203 | 609 × 304 | 1219 × 609 |
| 100 × 150 mm | 600 × 900 | 800 × 1200 | 1200 × 1800 | 2400 × 3600 |

### The size of the rendered image

The image the API returns follows a different rule, the same one Labelary uses: it counts whole dpi, 152, 203, 304 or 609 (dpmm × 25.4, rounded down), and multiplies them by the size in inches, rounding down again. So a 4 × 6 in label at 8 dpmm comes back as 812 × 1218 pixels, and at 12 dpmm as 1216 × 1824, slightly fewer than the physical dots above. Measured on the engine:

| Label | 6 dpmm | 8 dpmm | 12 dpmm | 24 dpmm |
|---|---|---|---|---|
| 4 × 6 in | 608 × 912 | 812 × 1218 | 1216 × 1824 | 2436 × 3654 |
| 4 × 2 in | 608 × 304 | 812 × 406 | 1216 × 608 | 2436 × 1218 |
| 2 × 1 in | 304 × 152 | 406 × 203 | 608 × 304 | 1218 × 609 |

One dot is one pixel, so a layout that uses every dot of the first table can lose its last row or column in the image: with ^LL1219 on a 4 × 6 in label at 8 dpmm, dot row 1218 falls outside the 1218-pixel image (rows 0 to 1217). Keep a margin of a few dots at the edges.

The label size pages have more sizes and a calculator.

## Fix 1: scale the label with ^MU

^MUD,200,300 tells the printer the coordinates were written for 200 dpi and should be scaled to 300. Put it right after ^XA. In the OpenZPL engine it multiplies positions, boxes and font sizes by 1.5, and the box is back to its 203 dpi size:

12 dpmm, no ^MU:
```zpl
^XA
^FO20,20^GB560,200,4^FS
^FO40,50^A0N,50,50^FDSame ZPL^FS
^FO40,120^A0N,30,30^FD560 x 200 dots box^FS
^XZ
```

12 dpmm with ^MUD,200,300:
```zpl
^XA
^MUD,200,300
^FO20,20^GB560,200,4^FS
^FO40,50^A0N,50,50^FDSame ZPL^FS
^FO40,120^A0N,30,30^FD560 x 200 dots box^FS
^XZ
```

It's the quickest fix for a carrier label written for 203 dpi. Check barcodes after scaling: bar widths are whole dots, and the printer has to round them.

## Fix 2: rewrite the coordinates

For a label you maintain, generate it for the target density: multiply every position, size and font height by 12 / 8 = 1.5 for 203 → 300 dpi, and set ^PW and ^LL from the table above. Or work in millimetres: with ^MUM every following coordinate is in millimetres and the label keeps its physical size on any density.

## Which density should I choose?

- 203 dpi is the default for shipping labels: carriers generate ZPL for it, and their barcodes are sized for it.
- 300 dpi pays off for small labels, small text (under about 6 pt) and dense 2D codes, such as jewellery tags or electronic component labels.
- 600 dpi is for very small labels and fine print; its printheads cost more and wear faster.

To find your printer's density, print a configuration label (usually by holding the feed button) and look for the resolution, or read it in the printer's web page. Then preview with the same density in the viewer.

**Why does my ZPL print smaller on a 300 dpi printer?** ZPL measures in dots and a 300 dpi dot is smaller: the same 560 dots are 70 mm at 203 dpi and 46.7 mm at 300 dpi. Scale with ^MUD,200,300 or rewrite the coordinates.

**Is 12 dpmm exactly 300 dpi?** No. 12 dots per millimetre are 304.8 dots per inch; 8 dpmm are 203.2.

**How many dots is a 4 × 6 in label at 203 dpi?** 812 × 1219 dots, rounding down: 4 × 203.2 = 812.8 and 6 × 203.2 = 1219.2, so ^PW812 and ^LL1219.