Actual-size online ruler
Measure directly on screen after calibration.
Measurement conversion tool
Convert ruler measurements between inches, cm, and mm
Use this converter when a ruler reading needs to move between inch fractions, decimal inches, centimeters, and millimeters. For actual-size screen measurement, calibrate the ruler before measuring.
Live conversion
1 in = 2.54 cm = 25.4 mm.
Conversion rules
Use millimeters when you need the finest common ruler unit.
Use centimeters for quick metric readings; 1 cm equals 10 mm.
Use inch fractions when matching hardware, fabric, and US product dimensions.
Convert before rounding when accuracy matters.
Common ruler fractions
These are the fraction marks most often found on inch rulers. Use the millimeter equivalent when you need to match a metric drawing or product spec.
| Fractional inch | Decimal inch | Millimeters |
|---|---|---|
| 1/16 in | 0.0625 in | 1.5875 mm |
| 1/8 in | 0.125 in | 3.175 mm |
| 3/16 in | 0.1875 in | 4.7625 mm |
| 1/4 in | 0.25 in | 6.35 mm |
| 5/16 in | 0.3125 in | 7.9375 mm |
| 3/8 in | 0.375 in | 9.525 mm |
| 7/16 in | 0.4375 in | 11.1125 mm |
| 1/2 in | 0.5 in | 12.7 mm |
| 5/8 in | 0.625 in | 15.875 mm |
| 3/4 in | 0.75 in | 19.05 mm |
| 7/8 in | 0.875 in | 22.225 mm |
| 1 in | 1 in | 25.4 mm |
Related ruler tools
All measurement guides
Browse every ruler guide, calculator, and converter in one place.
How to read a ruler
Learn inch fractions, centimeter marks, and millimeter ticks.
Online ruler calibration guide
Set the ruler scale before using actual-size screen measurements.
Screen PPI calculator
Estimate screen pixels per inch and pixels per millimeter.