100 × 50 mm
50 mm
Printing opens your browser's print dialog. In it, choose your thermal printer and set:
• Margins: None • Scale: 100% / Actual size • Background graphics: on
The page is already declared as @page { size: ; margin: 0 } in millimetres,
so 1 label = 1 physical label at the right size. DPI only affects sharpness, never the physical dimensions.