Display scale changed since you calibrated — measurements may be off.

Drop a real-size object

Click to add · drag to position · ✕ on the object to remove.

Your display

Derived from your calibration — accurate only at 100% zoom.

Match this outline to a real card held against the screen

Calibrate your screen

Your browser can't know your screen's real size, so we measure it once. Hold a bank / ID card flat against the screen and resize the outline in the corner until it matches exactly. Then it's cached for next time.

Tip: keep browser zoom at 100% for accuracy.