SAE to Metric Calculator & Metric to Standard (2024)

Convert a measurement from SAE to metric or metric to standard SAE using the calculator below. Learn more about SAE and metric measurements, and refer to the conversion chart below.

How to Convert SAE to Metric

SAE, or standard, and metric sockets, wrenches, and fasteners are both commonly used, but the difference between them is significant. Before we explain how to convert SAE to metric, it’s important to understand what these terms actually mean.

SAE stands for Society of Automotive Engineers,^[1] and is based on standard imperial and U.S. customary measurement systems. It uses measurements in inch fractions and is most commonly used in the United States.

The metric system was developed more recently and is commonly used worldwide. Metric sockets and screws are primarily measured in millimeters.

You can use the chart below to convert an SAE size to metric. You can also do the conversion by hand in a few easy steps as follows:

Step One: Convert the Inch Fraction to an Inch Decimal

The first step is to convert the inch fraction to a decimal. You can do this by treating the fraction as a division problem and solving it.

For instance:
1/4″ = 1 ÷ 4 = 0.25″

Step Two: Convert the Inch Decimal to Millimeters

The next step is to multiply the inch decimal by 25.4 to convert it to millimeters. This is the key step for converting SAE to metric.

0.25″ × 25.4 = 6.35 mm

SAE to Metric Conversion Chart

The chart below shows SAE measurements (in fractions) and the equivalent metric and inch decimal measurements for common socket, wrench, and screw sizes.

More Standard to Metric Conversions

You can use our inches to mm conversion calculator to convert SAE measurements to metric. You can also convert these common sizes by using the links below: