Bolt Size to Wrench Size Chart: A Handy Guide

Mastering the Bolt Size to Wrench Size Chart: A Practical Guide

Whether you’re a DIY enthusiast or a professional mechanic, understanding how to use a Bolt Size to Wrench Size Chart can save you time and frustration. This guide will help you navigate these charts efficiently, ensuring you always have the right tool for the job.

The relationship between bolt size and wrench size is based on the bolt’s head or nut size, which determines the appropriate wrench size needed to turn it. Here’s how they relate:

Bolt Diameter vs. Wrench Size: The wrench size refers to the distance across the flats of the bolt head or nut, also known as the “across flats” (AF) dimension. The bolt diameter is different from this dimension. For instance, a bolt with a diameter of 3/8″ does not use a 3/8″ wrench but rather a larger wrench size that matches the bolt head.

Standard (SAE) vs. Metric: The SAE (Society of Automotive Engineers) system uses inches, while the metric system uses millimeters. Standard wrench sizes correspond to specific bolt head sizes. For example, a 3/8″ bolt in SAE might require a 9/16″ wrench, while an M10 bolt in the metric system might need a 17mm wrench.

Bolt Grades and Head Sizes: Bolt head sizes can vary depending on the grade or type of bolt. Higher-grade bolts often have larger heads for a given diameter, which requires a larger wrench size.

SAE Fractional bolt size to wrench size

1/4 -> 7/16 wrench
5/16 -> 1/2 wrench
3/8 -> 9/16 wrench
7/16 -> 5/8 wrench
1/2 -> 3/4 wrench
9/16 -> 1-3/16 wrench
5/8 -> 1-5/16 wrench
3/4 -> 1- 1/8 wrench
7/8 -> 1- 5/16 wrench

8.8 DIN Metric bolt size to wrench size

M4 x .70 -> 7mm wrench
M5 x .80 -> 8mm wrench
M6 x 1.0 ->10mm wrench
M7 x 1.0 ->11mm wrench
M8 x 1.0 Fine -> 13mm wrench
M8 x 1.25 Standard ->13mm wrench
M10 x 1.0 Extra Fine ->17mm wrench
M10 x 1.25 Fine ->17mm wrench
M10 x 1.50 Standard ->16mm wrench
M12 x 1.25 Extra Fine ->19mm wrench
M12 x 1.50 Fine ->19mm wrench
M12 x 1.75 Standard ->19mm wrench
M14 x 1.50 Fine ->21mm wrench
M14 x 2.0 Standard ->21mm wrench
M16 x 2.0 ->24mm wrench
M18 x 2.5 ->27mm wrench
M20 x 2.5 ->30mm wrench
M22 x 2.5 ->32mm wrench
M24 x 3.0 ->36m wrench

10.9 DIN Metric bolt size to wrench size

M6 x 1 ->10mm wrench
M7 x 1.0 ->11mm wrench
M8 x 1.125 ->13mm wrench
M10 x 1.0 Extra Fine -> 17mm wrench
M10 x 1.25 Fine -> 17mm wrench
M10 x 1.50 Standard ->d 17mm wrench
M12 x 1.50 Fine -> 19mm wrench
M12 x 1.75 -> 19mm wrench
M14 x 2.00 -> 21mm wrench
M16 x 2.00 -> 24mm wrench
M20 x 2.50 -> 30mm wrench
M24 x 3.00 -> 36mm wrench

©, 2023 Rick Muscoplat