Digital Caliper
Measures diameter and length to 0.01 mm. The single most useful fastener tool.
Buy on AmazonHead Type
Drive Type
Measurements
Don't have calipers? Use our on-screen ruler
Calibrate first: hold a credit card (85.6 mm wide) against the ruler below and adjust the slider until they match.
Common Sizes — Quick Reference
Click any preset to populate the tool.
Articles & Guides
Learn how to measure, identify, and buy fasteners with confidence.
How to Measure a Screw
Diameter, length, pitch — what to measure and where from, with diagrams.
ReadMetric vs Imperial Fasteners
Why M6 and 1/4" look identical, and how to tell them apart in seconds.
ReadThread Pitch Explained
Coarse vs fine, TPI vs mm — everything you need to match a nut to a bolt.
ReadIdentify a Screw by Head Type
Visual field guide to every common head shape and its typical use.
ReadA Guide to Every Drive Type
Phillips, Torx, Robertson, Pozidriv — which one you actually have.
ReadRecommended Measuring Tools
Workshop-grade gear for exact fastener identification.
Thread Pitch Gauge
Set of metric + imperial blades. Instantly confirms pitch or TPI on any thread.
Buy on AmazonThread Checker Kit
Threaded holes + posts labeled with every common size. Screw-it-in-until-it-fits.
Buy on Amazon