Régua Digital was built to solve a real technical problem: mobile browsers don't know the physical size of the screen. Without correction, 1 cm drawn in the browser is almost never 1 cm in real life. Our tool fixes that with precision engineering — automatic device detection, a database of hundreds of models (iPhone, Galaxy, Redmi, Motorola, iPad, laptops and monitors), and fine calibration with a standard card or screen diagonal.
This free actual size screen ruler helps thousands of users measure ring size on screen, check shoe and foot size, and read millimeters and inches directly on their display. Whether you need to confirm a ring's inner diameter before ordering online, compare screws and coins, or measure small craft objects — everything happens with no app download, no sign-up, and no fees.
How it works
When you open the page, the calibration engine identifies your device and adjusts pixel density (PPI) automatically. For maximum accuracy, pick your exact model from the device database or calibrate with a standard credit card (85.60 × 53.98 mm). The scale then sits flush against the real screen edge — top, bottom, left or right — and you can switch between centimeters, millimeters, inches and pixels in one tap.
Why it's free
We believe measuring something small shouldn't require a heavy app or a purchase. Régua Digital is supported by discreet ads (Google AdSense), which keeps it 100% free, forever. Your calibration is stored only on your device — nothing is sent to our servers.
Need help? Reach us via our contact page or go back to the ruler and start measuring now.