3 millimeters Ruler — Actual Size
Use this ruler to visualize and measure exactly 3 millimeters on your screen. After calibrating with a credit card or reference object, the ruler above displays 3 mm at its true physical size on any device — phone, tablet, or desktop.
Unit Conversions for 3 millimeters
0.30
centimeters
3.0
millimeters
0.12
inches
How to Measure 3 millimeters
- Open this page on the device you want to measure with and use the ruler displayed above.
- Calibrate by placing a credit card on the screen and adjusting the slider until the outline matches the card. This takes about 10 seconds.
- Place the object you want to measure against the ruler. The markings show centimeters, millimeters, and inches, so you can read 3 mm directly.
- Your calibration is saved in the browser, so the ruler remains accurate on your next visit.
About This Measurement
3 millimeters equals 3.0 millimeters or 0.12 inches. One millimeter is one-thousandth of a meter, or about 0.039 inches. Millimeters are used for precise measurements in engineering, manufacturing, and science.