GaugeFox: Bolt & Thread Gauge

Need to find the size of an unknown bolt, screw, nut, drill bit, tap or pipe?
GaugeFox turns a calibrated Android screen into a practical bolt and thread gauge, then pairs each measurement with searchable Metric and Inch/SAE reference data.

MEASURE HARDWARE ON SCREEN

Calibrate with a standard payment or ID card, then place a clean part against the true-size guides.

- Identify bolt and screw shaft diameter in Metric or Inch/SAE sizes
- Match Metric thread pitch or Inch/SAE threads per inch (TPI)
- Check head profile, drive type and optional fastener length
- Measure drill bits and straight-thread taps, including tap pitch
- Check pipe and tube outside diameter, wrap measurements and common NPT sizes
- Measure nuts, bolt heads, open-end wrenches, six-point sockets and washer holes

FIND TAP AND DRILL SIZES

Search common Metric, UNC and UNF threads such as M6 x 1 or 1/4-20. See a starting tap-drill recommendation, nearby Metric or Inch/SAE alternatives, and ISO 273 close, normal and free clearance-hole sizes. Drill labels include Metric, Number, Letter and Fractional series where applicable.

SEARCH THE LIBRARIES

Look up fasteners, tool openings, washers, pipe sizes, thread data, head and drive tool sizes, and related drill information in one searchable reference. Nearby sizes make it easier to compare a close match without starting over.

SAVE WHAT YOU FOUND

Keep measurements, quantities and notes in the on-device Parts Bin. Open a precise retailer or web search for the displayed size when you need a replacement.

BUILT FOR THE WORKBENCH

- No account required
- Core gauges and reference tables work offline
- Measurement drafts and Parts Bin entries stay on your device
- Light and dark themes
- Responsive layouts for phones, tablets and foldable screens
- Banner ads stay off calibration and active measurement screens

An optional one-time Google Play purchase removes banner ads. It is not a subscription, and every tool remains available without buying it.

On-screen sizing is a practical identification aid, not a manufacturing inspection or safety certification. Confirm markings, fit, material, pressure rating, drill recommendations and applicable standards before installation or high-load use.