Conversion formula
Nearest rounding usually minimizes dimensional error. Floor keeps a result from exceeding a boundary; ceiling keeps it from falling below one.
Dots = millimetres × actual dots/mm
Dots = millimetres ÷ 25.4 × actual DPI
Actual millimetres = integer dots ÷ actual dots/mmCommon metric conversions
| Size | 8 dots/mm | 12 dots/mm | 24 dots/mm |
|---|---|---|---|
| 25.4 mm / 1 in | 203 dots | 305 dots | 610 dots |
| 50 mm | 400 dots | 600 dots | 1,200 dots |
| 100 mm | 800 dots | 1,200 dots | 2,400 dots |
| 150 mm | 1,200 dots | 1,800 dots | 3,600 dots |
Worked example at 12 dots/mm
A 50 mm dimension converts to exactly 600 dots. Converting 600 dots back at 12 dots/mm returns exactly 50 mm, with zero raster-rounding error.
Raster versus mechanical accuracy
The formula describes the nominal raster. Media movement, printhead alignment, calibration and manufacturing tolerances can still shift output. Measure a test print where exact placement matters.
Frequently asked questions
Can a 12 dots/mm format print unchanged at 8 dots/mm?
No. The same dot coordinates produce another physical size, so dimensions and barcode modules must be recalculated.
Why does 8 dots/mm equal 203.2 DPI?
One inch is exactly 25.4 mm, so 8 × 25.4 equals 203.2 dots per inch. “203 DPI” is the nominal product label.
Run the calculation
Use your own measurements in the browser-based calculator. Inputs are processed locally and are not uploaded to LabelOps Lab.
Open the Printer Dots CalculatorRelated guides
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