These were mostly created in Gimp 2 with the font "Allerta Stencil," and then converted to .stl files in Tinkercad. Please feel free to edit and create your own.

The smallest circle on the left is the same font size as the letters/numbers and can be used as a decimal point (for example, the dot in "3.5 years.")

The manufacturer of my child's growth chart decided to make it waterproof, so my pen ink smudges until it dries if my hand swipes it (cotton swabs help with cleanup.) If you want to use permanent marker or paint, you might consider enlarging the stencil a bit for wider holes if the tip is bigger than a pen.