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Reading guide
Worked example5 cm = 50 mm = approximately 1.968504 in
| Centimeters | Inches | Meaning |
|---|---|---|
| 2.54 cm | 1 in | Exact definition |
| 5 cm | 1.968504 in | Rounded to six decimals |
| 5.08 cm | 2 in | Exact conversion |
| 10.16 cm | 4 in | Exact conversion |
A ruler with centimeters and inches together
Keep dual scales enabled to see centimeters along the top edge and inches along the bottom. Their origins share the same horizontal position, so a vertical target guide intersects the same length on both scales. Left and right edges, when enabled, use centimeters and inches respectively. The inch scale uses sixteenths, while the centimeter scale uses millimeter subdivisions.
Compare a metric object with an imperial specification
Suppose a craft instruction calls for a 2-inch strip but your material is described in centimeters. Two inches equal exactly 5.08 cm. Type 5.08 in the centimeter input and compare the single target line with the inch scale. This avoids interpreting 5 cm as exactly 2 inches: the difference is 0.8 mm. Disable dual scales or select another unit to return to ordinary single-unit labels.
Screen measurements and image measurements differ
This tool measures a physical distance against the calibrated display. It does not infer an object’s real-world dimensions from a photograph. A zoomed image can look larger or smaller without changing the screen scale. For an image, establish its own known size reference or use the original drawing dimensions; screen calibration alone cannot determine the object’s real-world scale.
How this ruler works
The scale uses your current calibration in CSS pixels per inch. Metric ticks divide that density by 25.4; inch ticks divide it by 16. Conversions use the exact definition 1 inch = 25.4 mm. The target keeps its entered length rather than stretching to fill the display.
Keep browser zoom at 100%, verify with a known reference, and recheck after changing screens. Inputs stay in your browser; no camera, account, or upload is required. For critical dimensions, use a suitable calibrated physical instrument.
Methodology, calibration help, and measurement support: Accuracy methodology · Calibrate screen · Contact us. Unit definitions: NIST.