In the print dialog choose Scale 100% (or 'Actual size') and turn off 'Fit to page'. After printing, always check the size against the card outline.

Marker Sheet v1From Burr to Tongue · oosioo.comPrint at actual size (100%)Measurement window 120 × 80 mm · spread grounds inside, not touching012345678910cmHorizontal 100 mm scale · check against a steel rulerCard outline 85.60 × 53.98 mmLay a bank card, transit card or ID card on it and check all four edgesIf any edge is off by more than 1 mm, print againPrint scale check012345678910Vertical 100 mm scaleHow to shoot1. Print on matte paper with 'Fit to page' off at 100% scale2. Check the scale with the card and both rulers3. Tape the sheet flat to a flat surface4. Spread the grounds inside the window5. Shoot from above with the phone's main camera, with all four markers near the frame centre6. Do not use macro mode or zoomMarkers: ArUco DICT_4X4_50ID 0 top left · 1 top right · 2 bottom right3 bottom left · 12 mm side · centres 144 × 104 mmFree to print and use · CC BY 4.0 oosioo.com · Sizes on screen are not actual size