How do I determine the correct bolt size for my project?

Measure the following to determine the correct bolt size:

• Diameter: The size of the bolt or hole where the bolt goes.
• Length: Gauge the entire length, encompassing the head if it rests evenly or above the top.
• Thread Length: Ensure the threaded portion is sufficient to secure the materials being fastened.
• Strength Requirements: Look for the grade or class of the bolt (like Grade 2, Grade 5, Grade 8 in SAE; Class 8.8,10.9 in metric) to ensure it fulfills the strength specifications needed for its use.