Also known as a 10 thou blade.
Feeler Gauge Converter
Convert feeler gauge thickness between inches, millimeters, thou, mils, and microns. Use the presets for common blades or build a simple blade stack for a target gap.
Convert a feeler gauge thickness
Enter the number printed on your blade or choose a common preset. Results update instantly.
A 0.010 inch feeler gauge is 0.254 mm, 10 thou, and 254 microns.
Blade stack helper
Enter a target gap and get a simple combination from common inch blades.
0.010 + 0.008 in
Total: 0.018 in / 0.457 mm.
How to read feeler gauge sizes
Feeler gauges may be marked in inches, millimeters, or both. Inch blades are often spoken as “thou” or “mils,” where 1 thou equals 0.001 inch. Metric blades are usually labeled directly in millimeters.
- 0.010 inch = 10 thou = 0.254 mm
- 0.20 mm ≈ 0.0079 inch ≈ 7.9 thou
- 100 microns = 0.100 mm ≈ 0.00394 inch
Common uses
This converter is useful for spark plug gaps, valve lash checks, points gaps, guitar setup, machine setup, and any job where a small mechanical clearance is specified in a different unit than your gauge set.
For critical mechanical work, always follow the service manual and use clean, undamaged blades.
Common feeler gauge conversion chart
| Inches | Millimeters | Thou / mils | Microns |
|---|
Feeler gauge conversion FAQ
Is mil the same as mm?
No. A mil is one thousandth of an inch, also called one thou. A millimeter is metric and equals about 39.37 mils.
What is 0.001 inch in millimeters?
0.001 inch is 0.0254 mm, or 25.4 microns.
Should I use the inch or metric side of my gauge?
Use the unit specified by the manual or drawing when possible. If the specification is in the other unit, convert it here and choose the nearest blade or blade stack.