Actual Size Online Ruler (cm, mm & inches)
Measure real objects directly on your screen with dual-caliper precision. Supports metric millimeters & centimeters, fractional 1/16" imperial inches, 2D area box measurement, and 1-click bank card calibration.
CM, MM, Inches & Pixels Converter
Instantly convert between metric, imperial fractions, and screen pixels at your calibrated 96.0 PPI.
Standard Everyday Object Sizes (Measure & Verify)
Click any item below to automatically set the ruler calipers to its exact real-world size.
| Everyday Object | Millimeters | Centimeters | Inches | Action |
|---|---|---|---|---|
| Credit / Bank Card (Width) | 85.6 mm | 8.56 cm | 3.370" (3 3/8") | |
| Credit / Bank Card (Height) | 53.98 mm | 5.4 cm | 2.125" (2 1/8") | |
| US Quarter Coin (Diameter) | 24.26 mm | 2.43 cm | 0.955" (15/16") | |
| US Penny Coin (Diameter) | 19.05 mm | 1.91 cm | 0.750" (3/4") | |
| 1 Euro Coin (Diameter) | 23.25 mm | 2.33 cm | 0.915" | |
| AA Battery (Length) | 50.5 mm | 5.05 cm | 1.988" (~2") | |
| Standard Paperclip (Length) | 33 mm | 3.3 cm | 1.300" (1 5/16") | |
| A4 Paper (Short Side Width) | 210 mm | 21 cm | 8.268" (8 1/4") |
How to Measure Anything in Actual Size on Your Screen
Calibrate with a Bank Card or Screen Size
Click "Calibrate to Actual Size" and hold any standard credit card (85.6 mm) or coin against your screen, or select your laptop/monitor diagonal size in inches.
Place Your Object & Drag Calipers A & B
Hold your physical item flush against the screen. Drag the green A and red B caliper handles to read exact millimeters, centimeters, and 1/16" fractional inches.
Pin, Copy & Convert Measurements
Switch between the 1D Dual-Edge Ruler, 2D Width × Height Box, and 180° Protractor. Pin measurements to your browser history with custom labels for easy comparison.
Frequently Asked Questions — Online Ruler (Actual Size)
Is this online ruler accurate to actual physical size?
Yes. Once calibrated with a standard bank/credit card (ISO 85.60 mm width) or your display's diagonal size in inches, our online ruler calculates your exact screen Pixels Per Inch (PPI) and renders 1:1 true-to-life millimeter, centimeter, and 1/16-inch graduations.
Can I use both centimeters (cm) and inches on the same ruler?
Yes! The top edge displays metric centimeters (cm) and millimeters (mm), while the bottom edge displays imperial inches with 1/2, 1/4, 1/8, and 1/16 fractional markings simultaneously.
Does browser zoom affect the online ruler accuracy?
For automatic screen detection, keep your browser zoom at 100% (press Ctrl+0 or Cmd+0). If you calibrate manually using a physical credit card or coin against your screen, the ruler remains 100% accurate at your current zoom level.
Does my calibration stay saved for next time?
Yes, your calibrated PPI setting and pinned measurements are saved locally in your browser's localStorage so the ruler is immediately ready in actual size every time you visit.