3D acceleration unavailable — showing a flat, true-to-size preview instead.
Your browser can't tell us this — pick whichever method you can do right now.
Hold a payment card (or ID card) up to the screen. Resize the box until it matches exactly.
Measure this bar with any ruler or tape measure, in any unit, then type what you measured.
Approximate — fails if your OS uses display scaling. Enter your screen's diagonal size in inches.
Approximate starting guess based on your device — please confirm or correct it.
If you already know your screen's pixel density:
This bar should measure exactly 100 mm (≈3.94 in). Check it with your ruler.