Bolt Size Lookup
Search bolt and screw sizes by model number, or browse by category. Find dimensions, thread pitch, materials, and standards instantly.
About Bolt Standards
Bolts and screws are manufactured according to international standards that define their dimensions, mechanical properties, and testing methods. The three most common standard systems are:
- GB (Guobiao) — China's national standards, such as GB/T 5782 for hex bolts and GB/T 70.1 for socket head cap screws
- DIN (Deutsches Institut fur Normung) — German industrial standards widely used across Europe, such as DIN 933 for hex bolts and DIN 912 for socket head cap screws
- ISO (International Organization for Standardization) — International standards like ISO 4017 for hex bolts and ISO 4762 for socket head cap screws
Common Bolt Types
- Hex Bolts — The most common fastener type, featuring a six-sided head. Available in various strength grades (4.8, 8.8, 10.9, 12.9) and materials.
- Socket Head Cap Screws — High-strength bolts with a cylindrical head and internal hexagonal drive. Used in precision machinery and high-load applications.
- Flange Bolts — Hex bolts with an integrated washer-like flange that distributes clamping force over a wider area.
- Self-Tapping Screws — Screws that form their own threads when driven into materials like sheet metal, plastic, or wood.
- Expansion Bolts — Anchoring fasteners designed for mounting objects to concrete or masonry walls.
- Set Screws — Headless screws used to secure objects within or against another component, commonly used with shafts and collars.
Understanding Metric Bolt Designations
Metric bolt sizes follow a standard notation: M[diameter]x[length], for example M8x30 means a bolt with an 8mm nominal diameter and 30mm length. The thread pitch (distance between threads) is standardized for each diameter. Coarse thread is the default, while fine thread variants are also available for applications requiring higher precision or vibration resistance.