Calibrate

How to Calibrate Your Screen

Calibration measures your screen's pixel density (DPI) so we can display objects at their true physical size. It takes about 10 seconds and only needs to be done once.

01

💵 Local Currency Note — Recommended

Use a common banknote from your country

  1. Click Calibrate with Currency Note below
  2. Place your real banknote flat against your screen
  3. Drag the corner of the guide to match your note exactly
  4. Click Use This Note
Why this works: Banknotes have known standard dimensions. Matching pixels to this known size gives us your exact DPI.
02

💳 Credit Card — Universal Alternative

Works for any standard bank card or ID card

  1. Click Calibrate with Credit Card below
  2. Place your credit card flat against your screen
  3. Drag the corner of the guide to match your card exactly
  4. Click Apply This Calibration
Why this works: All standard credit cards are exactly 85.60 mm wide (ISO/IEC 7810 ID-1). Matching pixels to this known size gives us your exact DPI.
03

🖥️ Monitor Size

Useful if you don't have a card or banknote available

  1. Click Calibrate with Monitor Size below
  2. Find your monitor's diagonal size (usually printed on the box or in specs)
  3. Enter the size in inches and click Apply
Note: May be less accurate on HiDPI/Retina displays due to CSS pixel scaling.

Frequently Asked Questions

Is the calibration stored permanently?
Yes — your calibration is saved to your browser's localStorage. It persists across visits until you reset it or clear your browser data. If you use a different browser or device, you'll need to calibrate again.
Why is my phone the wrong size?
Mobile browsers scale CSS pixels independently of physical pixels. Calibrating on a phone with a credit card gives the best result. Monitor diagonal input is not recommended on phones.
What DPI should my screen be?
Common values: 96 DPI (standard HD monitors), 109 DPI (27" 1080p), 163 DPI (standard Retina MacBook), 227 DPI (5K iMac). Your DPI is shown in the calibration bar after calibrating.
Can I use any card for calibration?
Yes — any standard credit card, debit card, driver's license, or government ID card. All follow the ISO 7810 ID-1 standard: exactly 85.60 × 53.98 mm.
Can I use a banknote instead of a card?
Yes — the Currency Note method uses a local banknote from your country. When supported, simply select your country and note, then match its width on screen. Banknotes have legally standardized dimensions, making them reliable calibration references.