Wrench Size Chart: SAE to Metric Socket and Wrench ConversionFractional inch wrench sizes with decimal inch, exact mm, and nearest common metric references
Use this wrench size chart to compare SAE fractional wrench and socket sizes with decimal inches, exact millimeter conversion, and the closest common metric wrench or socket size. The inch-to-mm value is exact; the closest metric size is only a practical fit reference and must be verified against the fastener, tool clearance, wear, coating, torque, and safety requirement.
Exact Unit Conversion
Every SAE size includes decimal inch and exact millimeter values based on 1 inch = 25.4 mm.
Nearest Metric Reference
Compare each fractional wrench size with a common metric wrench or socket size, with the difference shown in millimeters.
Shop-Floor Caveats
Use close sizes for planning only. Final tool choice depends on fastener standard, head style, wear, coating, and safety requirements.
Answer first: SAE wrench sizes to metric
SAE wrench sizes convert to millimeters by multiplying the decimal inch size by 25.4. For example, 1/2 inch is exactly 12.700 mm and is commonly compared with a 13 mm wrench or socket; 3/4 inch is exactly 19.050 mm and is commonly compared with 19 mm.
These closest metric values are practical references, not guaranteed substitutes.
Search, Print & Export
Showing 28 SAE tool-size rows. On small screens, swipe the table horizontally to see all columns.
SAE to metric wrench and socket size chart
Search or scan common SAE fractional sizes from 1/4 inch to 2 inch. Exact mm is calculated from inch × 25.4; nearest metric is a practical reference.
| SAE wrench/socket size | Decimal inch ↑ | Exact mm | Closest common metric | Difference | Fit note |
|---|---|---|---|---|---|
| 1/4" | 0.25000 | 6.350 mm | 6 mm | -0.350 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 5/16" | 0.31250 | 7.938 mm | 8 mm | +0.062 mm | Very close reference; still verify actual fastener fit. |
| 11/32" | 0.34375 | 8.731 mm | 9 mm | +0.269 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 3/8" | 0.37500 | 9.525 mm | 10 mm | +0.475 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 7/16" | 0.43750 | 11.112 mm | 11 mm | -0.112 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 1/2" | 0.50000 | 12.700 mm | 13 mm | +0.300 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 9/16" | 0.56250 | 14.287 mm | 14 mm | -0.287 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 5/8" | 0.62500 | 15.875 mm | 16 mm | +0.125 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 11/16" | 0.68750 | 17.462 mm | 17 mm | -0.462 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 3/4" | 0.75000 | 19.050 mm | 19 mm | -0.050 mm | Very close reference; still verify actual fastener fit. |
| 13/16" | 0.81250 | 20.637 mm | 21 mm | +0.363 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 7/8" | 0.87500 | 22.225 mm | 22 mm | -0.225 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 15/16" | 0.93750 | 23.813 mm | 24 mm | +0.187 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 1" | 1.00000 | 25.400 mm | 25 mm | -0.400 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 1-1/16" | 1.06250 | 26.987 mm | 27 mm | +0.013 mm | Very close reference; still verify actual fastener fit. |
| 1-1/8" | 1.12500 | 28.575 mm | 29 mm | +0.425 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 1-3/16" | 1.18750 | 30.162 mm | 30 mm | -0.162 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 1-1/4" | 1.25000 | 31.750 mm | 32 mm | +0.250 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 1-5/16" | 1.31250 | 33.337 mm | 33 mm | -0.337 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 1-3/8" | 1.37500 | 34.925 mm | 35 mm | +0.075 mm | Very close reference; still verify actual fastener fit. |
| 1-7/16" | 1.43750 | 36.512 mm | 36 mm | -0.512 mm | Large difference; do not treat as a tool substitution without direct fit verification. |
| 1-1/2" | 1.50000 | 38.100 mm | 38 mm | -0.100 mm | Very close reference; still verify actual fastener fit. |
| 1-5/8" | 1.62500 | 41.275 mm | 41 mm | -0.275 mm | Close practical reference; check for looseness, wear, coating, and clearance. |
| 1-11/16" | 1.68750 | 42.862 mm | 42 mm | -0.862 mm | Large difference; do not treat as a tool substitution without direct fit verification. |
| 1-3/4" | 1.75000 | 44.450 mm | 46 mm | +1.550 mm | Large difference; do not treat as a tool substitution without direct fit verification. |
| 1-13/16" | 1.81250 | 46.037 mm | 46 mm | -0.037 mm | Very close reference; still verify actual fastener fit. |
| 1-7/8" | 1.87500 | 47.625 mm | 48 mm | +0.375 mm | Noticeable difference; use for planning only and verify before applying torque. |
| 2" | 2.00000 | 50.800 mm | 50 mm | -0.800 mm | Large difference; do not treat as a tool substitution without direct fit verification. |
Nearest metric size = closest common nominal tool size by millimeter difference, not a guaranteed substitute.
How to read the wrench size conversion chart
- Find the SAE fractional wrench or socket size.
- Read the decimal inch value.
- Multiply by 25.4 to get exact millimeters.
- Compare with the closest common metric size.
- Verify real fit on the fastener before use.
Important fit note
The inch-to-millimeter conversion in this chart is exact. The “closest common metric” column is only a practical shop-floor reference. It does not mean an SAE wrench, metric wrench, SAE socket, or metric socket is guaranteed to fit or safely substitute for another tool. Actual fit depends on the fastener standard, head style, tolerance, wear, coating, corrosion, tool clearance, torque requirement, and safety context.
Common SAE to metric wrench examples
These examples use exact inch-to-mm conversion and closest common nominal metric tool sizes. Always verify the actual fastener before applying torque.
1/2 inch wrench to mm
1/2 inch is exactly 12.700 mm; the closest common metric reference is 13 mm, which is +0.300 mm larger.
Verify before use9/16 inch wrench to mm
9/16 inch is exactly 14.287 mm; the closest common metric reference is 14 mm, which is -0.287 mm smaller.
Verify before use3/4 inch wrench to mm
3/4 inch is exactly 19.050 mm; the closest common metric reference is 19 mm, which is -0.050 mm smaller.
Verify before use1 inch wrench to mm
1 inch is exactly 25.400 mm; the closest common metric reference is 25 mm, which is -0.400 mm smaller.
Verify before useWhen a close metric size may or may not work
Lower-risk comparison use cases
Planning, tool inventory, identifying missing tool sizes, and non-critical shop-floor comparison where no torque or safety decision is made from the chart alone.
Do not treat as automatic substitution
Rounded fasteners, worn heads, high torque, safety-critical assemblies, precision work, corroded or coated hardware, and tight tool clearance require direct fit and engineering judgment.
Formula and reference assumptions
- Exact conversion: mm = inch × 25.4.
- Difference: difference = closest common metric mm − exact mm.
- Rounding: Decimal inches display to 5 places; exact millimeters and differences display to 3 decimals.
- Reference scope: Exact unit conversion plus common metric nominal tool-size references cross-checked against common shop-floor reference charts and standard nominal size lists.
- Last reviewed: 2026-07-06.
Wrench Size Chart FAQ
What is a wrench size chart?
A wrench size chart compares nominal wrench or socket sizes across measurement systems. This page shows SAE fractional sizes, decimal inches, exact millimeters, and the closest common metric wrench or socket size for quick reference.
How do you convert an SAE wrench size to millimeters?
Convert the fractional inch size to decimal inches, then multiply by 25.4. For example, 1/2 inch equals 0.500 inch, so 0.500 × 25.4 = 12.700 mm.
What metric wrench is closest to 1/2 inch?
1/2 inch is exactly 12.700 mm. The nearest common metric wrench or socket size is usually 13 mm, which is 0.300 mm larger than the exact inch conversion.
What metric socket is closest to 9/16 inch?
9/16 inch is exactly 14.287 mm. The nearest common metric socket size is usually 14 mm, which is 0.287 mm smaller than the exact inch conversion.
Is 3/4 inch the same as 19 mm?
No. 3/4 inch is exactly 19.050 mm. A 19 mm wrench or socket is very close, but it is still 0.050 mm smaller than the exact conversion and should be verified on the actual fastener.
Can I use a metric wrench on an SAE bolt?
Sometimes a close metric wrench may fit an SAE fastener, but this chart does not guarantee safe substitution. Fit depends on head style, tolerance, wear, coating, corrosion, tool clearance, torque, and safety requirements.
Are SAE and metric sockets interchangeable?
No. SAE and metric sockets are different nominal size systems. Some sizes are close enough for comparison, but they should not be treated as fully interchangeable, especially for high-torque, worn, coated, or safety-critical fasteners.
Why does the chart show a difference column?
The difference column shows how far the closest common metric size is from the exact millimeter conversion. A small difference may be useful for planning, but it is still not a guarantee that the tool will fit safely.
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