Imperial measurement

Online Ruler Inches: Measure in Fractional and Decimal Inches

Read common fractional inch divisions or use decimal inches for physical sizing. Calibrate the display before treating the result as a real-world dimension.

Open Inch RulerCalibration Guide

Understanding the fractional inch scale

The inch mode divides each inch into common fractional intervals such as 1/2, 1/4, 1/8, and 1/16. Those fractions are exact mathematical subdivisions of an inch; the physical accuracy of the displayed ruler still depends on the screen scale.

  • 1/2 inch = 0.500 inch
  • 1/4 inch = 0.250 inch
  • 1/8 inch = 0.125 inch
  • 1/16 inch = 0.0625 inch

Fraction to decimal to millimeter

FractionDecimal inchMillimeters
1/160.06251.5875
1/80.12503.175
1/40.25006.35
1/20.500012.7
11.000025.4

How to measure in inches on screen

  1. Set browser zoom to 100%.
  2. Open the inch ruler.
  3. Calibrate against a known physical length for physical measurements.
  4. Align the object's edge with zero.
  5. Read the fractional or decimal inch value at the opposite edge.

Important distinction

1 inch equals exactly 25.4 mm. That unit conversion is exact; whether a displayed inch on a particular screen is physically one inch is a separate calibration question.