Online Ruler

help How to Use the Online Ruler

The ruler usually auto‑detects your device and displays accurate cm / inch scales. If detection fails, enter your screen size once or calibrate for pixel‑perfect dimensions.

1. 📱 Automatic Device Detection

Works out of the box—no setup.

• Recognises 250+ phone, tablet and laptop models.
• Applies the correct factory PPI.
• A green “Detected” box confirms accuracy.
• Settings persist between visits.

2. 💻 Set Your Screen's Diagonal

If auto‑detect fails, enter your screen’s diagonal or calibrate with a credit card. Your setting is saved for future visits.

Steps:

1. Find the diagonal size (check device box or online search online model name).
2. Enter it in Screen Diagonal.
3. Click Apply.

3. 💳 Calibrate with a Credit Card

All bank cards share a standard width (85.60 mm/3.37 in) this allow calibrate accurate size for the ruler.

Steps:

1. Calibrate > Open Credit Card calibration.
2. Place a card on the blue guide.
3. Adjust the slider until the guide matches the card.

devices Supported Devices and Browsers

Our online ruler works on all modern devices and browsers, with automatic detection for 250+ screens.

Supported Screens

• Apple: iPhone, iPad, MacBook, iMac, Studio Display
• Samsung: Galaxy S series, Note series, Fold/Flip devices
• Google: Pixel phones and tablets
• Windows: Surface Pro, Surface Laptop, Surface Book and Surface Go
• Monitors: Picked from the list — a 1920×1080 screen can be 22″ or 32″, so we never guess

Browser Compatibility

Works perfectly on:

• Chrome (desktop and mobile)
• Safari (iOS and macOS)
• Firefox (all platforms)
• Edge (Windows)
• Opera (all platforms)

If your device isn’t detected, use quick calibration or manual entry for accuracy.

verified Tips for Best Results

• Browser zoom is corrected automatically; avoid pinch-zooming on a phone.
• Re‑calibrate when switching devices or monitors.
• Make sure JavaScript is enabled — the ruler is drawn with it.