Socket Sizes mm to inches Conversion Chart
Complete conversion guide for metric and SAE socket sizes. Find the nearest socket equivalents and understand why you can't always substitute between measurement systems.
Metric Socket to SAE Equivalent
Find the nearest SAE (imperial) socket for your metric fasteners
| Metric Size | Decimal Inches | Nearest SAE |
|---|---|---|
| 6mm | 0.236" | 1/4" |
| 7mm | 0.276" | 1/4" |
| 8mm | 0.315" | 5/16" |
| 9mm | 0.354" | 3/8" |
| 10mm | 0.394" | 3/8" |
| 11mm | 0.433" | 7/16" |
| 12mm | 0.472" | 1/2" |
| 13mm | 0.512" | 1/2" |
| 14mm | 0.551" | 9/16" |
| 15mm | 0.591" | 5/8" |
| 16mm | 0.630" | 5/8" |
| 17mm | 0.669" | 11/16" |
| 18mm | 0.709" | 11/16" |
| 19mm | 0.748" | 3/4" |
| 21mm | 0.827" | 13/16" |
| 22mm | 0.866" | 7/8" |
| 24mm | 0.945" | 15/16" |
Important: Never Force a Socket
While some metric and SAE sizes are close, they are not interchangeable. Using the wrong size socket can:
- Round off bolt heads and nut corners
- Damage your sockets and fasteners
- Create safety hazards when fasteners fail
- Make future removal extremely difficult
Always use the correct measurement system. If a socket doesn't fit easily, it's the wrong size.
Understanding Socket Sizes Systems
Metric Sockets (mm)
Metric socket sizes are measured in millimeters and typically increase in whole number increments (6mm, 7mm, 8mm, etc.).
- Used on most vehicles made outside North America
- Standard on modern cars (post-1980s)
- Common sizes: 6mm to 24mm for automotive work
- Larger sizes used for heavy equipment
SAE Sockets (inches)
SAE (Society of Automotive Engineers) sockets use fractional inch measurements, typically in 1/16" increments.
- Traditional American standard
- Used on older American vehicles and equipment
- Common sizes: 1/4" to 1" for automotive work
- Still found on lawn equipment and machinery
Quick Conversion Tips
1
Memorize the conversion: 1 inch = 25.4mm exactly. This is the basis for all socket conversions.
2
Use our calculator: For precise conversions, use our mm to inches converter to see exact decimal values.
3
Visual check: Compare sockets side-by-side before using. Even small differences can cause damage.
4
Build both sets: Keep complete metric and SAE socket sets. The investment prevents frustration and damage.