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Automotive Repair
Cars use a mix of Metric (modern) and SAE (vintage/US) fasteners. This chart helps you switch between them.
- •Metric sizes for European/Asian cars
- •SAE for older American muscle
- •Common 10mm, 13mm, 1/2", 9/16" sizes
The ultimate workshop reference for matching wrenches to bolts. Instantly find the right spanner or socket for Hex Bolts, Heavy Hex, and Socket Cap Screws. Compare Metric and SAE sizes side-by-side.
Auto Mechanic • Metric & SAE • all
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Metric & SAE Wrench Comparison • A4
| Wrench Size | Actual (mm) | Metric Hex | SAE Hex | Metric Socket | SAE Socket | Heavy Hex |
|---|---|---|---|---|---|---|
| 0.050" | 1.27 | - | - | - | #3, #4 | - |
| 1.5mm | 1.50 | - | - | M1.6, M2 | - | - |
| 1/16" | 1.59 | - | - | - | #5, #6 | - |
| 5/64" | 1.98 | - | - | - | #8 | - |
| 2mm | 2.00 | - | - | M2.5 | - | - |
| 3/32" | 2.38 | - | - | - | #10, 1/8" | - |
| 2.5mm | 2.50 | - | - | M3 | - | - |
| 7/64" | 2.78 | - | - | - | #6 | - |
| 3mm | 3.00 | - | - | M4 | - | - |
| 9/64" | 3.57 | - | - | - | #8 | - |
| 5/32" | 3.97 | - | #6 (Small Pattern) | - | #10 | - |
| 4mm | 4.00 | - | - | M5 | - | - |
| 3/16" | 4.76 | - | #8 (Small Pattern) | - | 1/4" | - |
| 5mm | 5.00 | - | - | M6 | - | - |
| 5.5mm | 5.50 | M3 | - | - | - | - |
| 6mm | 6.00 | - | - | M8 | - | - |
| 1/4" | 6.35 | - | #6 | - | 5/16" | - |
| 7mm | 7.00 | M4 | - | - | - | - |
| 5/16" | 7.94 | - | #8, #10 | - | 3/8" | - |
| 8mm | 8.00 | M5 | - | M10 | - | - |
| 11/32" | 8.73 | - | #8 (Heavy), #10 (Small) | - | - | - |
| 3/8" | 9.52 | - | #10 (Heavy), 1/4" (Small) | - | 7/16", 1/2" | - |
| 10mm | 10.00 | M6 | - | M12 | - | - |
| 7/16" | 11.11 | - | 1/4" | - | - | - |
| 12mm | 12.00 | - | - | M14 | - | - |
| 1/2" | 12.70 | - | 5/16" | - | 5/8" | - |
| 13mm | 13.00 | M8 | - | - | - | - |
| 14mm | 14.00 | - | - | M16 | - | - |
| 9/16" | 14.29 | - | 3/8" | - | - | - |
| 5/8" | 15.88 | - | 7/16" | - | 3/4" | - |
| 16mm | 16.00 | M10 (ISO) | - | - | - | - |
| 17mm | 17.00 | M10 (DIN) | - | M20 | - | - |
| 18mm | 18.00 | M12 (ISO) | - | - | - | - |
| 19mm | 19.00 | M12 (DIN) | - | M24 | - | - |
| 3/4" | 19.05 | - | 1/2" | - | 7/8", 1" | - |
| 13/16" | 20.64 | - | 9/16" | - | - | - |
| 21mm | 21.00 | M14 (ISO) | - | - | - | - |
| 22mm | 22.00 | M14 (DIN) | - | - | - | - |
| 7/8" | 22.22 | - | - | - | - | 1/2" (Heavy) |
| 15/16" | 23.81 | - | 5/8" | - | - | - |
| 24mm | 24.00 | M16 | - | - | - | - |
| 27mm | 27.00 | M18 | - | - | - | - |
| 30mm | 30.00 | M20 | - | - | - | - |
| 32mm | 32.00 | M22 (DIN) | - | - | - | - |
| 34mm | 34.00 | M22 | - | - | - | - |
| 36mm | 36.00 | M24 | - | - | - | - |
| 1-1/8" | NaN | - | 3/4" | - | - | - |
| 1-5/16" | NaN | - | 7/8" | - | - | - |
| 1-1/2" | NaN | - | 1" | - | - | - |
| 1-1/16" | NaN | - | - | - | - | 5/8" (Heavy) |
| 1-1/4" | NaN | - | - | - | - | 3/4" (Heavy) |
| 1-7/16" | NaN | - | - | - | - | 7/8" (Heavy) |
| 1-5/8" | NaN | - | - | - | - | 1" (Heavy) |
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Stop stripping bolts with the wrong tool. Use this chart to find the perfect fit every time.
Measure the distance across the flats (parallel sides) of the bolt head or nut using calipers.
Locate the measurement in the chart. The corresponding Wrench Size is what you need.
If you don't have the exact metric wrench, check the SAE column for a close equivalent (and vice versa).
From the garage to the living room, know your tools.
Cars use a mix of Metric (modern) and SAE (vintage/US) fasteners. This chart helps you switch between them.
Construction equipment often uses large, heavy hex bolts that require specific heavy-duty wrenches.
Furniture assembly often relies on Socket Cap screws (Allen keys). Don't lose that little L-wrench!
The Short Answer: Rarely. While some sizes are very close (like 19mm and 3/4"), most are not interchangeable. Using the wrong wrench can round off the bolt head.
The Close Matches:
⚠️ Warning: Always try to use the correct system. Use substitutes only in emergencies and avoid high-torque applications.
The standard six-sided bolt. Driven by wrenches, sockets, or adjustable spanners.
Used in structural steel. The head is wider than a standard hex bolt for better load distribution.
Cylindrical head with an internal hex drive. Driven by Hex Keys (Allen Wrenches).
| Size | Pitch/TPI | Head |
|---|---|---|
| M3 | 0.5 | 5.5 |
| M4 | 0.7 | 7.0 |
| M5 | 0.8 | 8.0 |
| M6 | 1.0 | 10.0 |
| M8 | 1.25 | 13.0 |
| 1/4" | 20 | 7/16" |
| 5/16" | 18 | 1/2" |
| 3/8" | 16 | 9/16" |
Metric and imperial bolt, screw, and thread pitch reference.
| Number | Fraction | Decimal (in) | Millimeters |
|---|---|---|---|
| #80 | — | 0.0135 | 0.34 |
| #50 | — | 0.0700 | 1.78 |
| #52 | 1/16" | 0.0625 | 1.59 |
| #41 | 3/32" | 0.0938 | 2.38 |
| #22 | 5/32" | 0.1562 | 3.97 |
| #11 | 3/16" | 0.1875 | 4.76 |
| #7 | 13/64" | 0.2031 | 5.16 |
| — | — | 0.2570 | 6.53 |
| — | 3/8" | 0.3750 | 9.53 |
| — | 1/2" | 0.5000 | 12.70 |
Numbered, lettered, metric, and fractional drill bit reference.
| Millimeters | Decimal (in) | Fraction (in) |
|---|---|---|
| 0.5 | 0.020 | 0 |
| 1 | 0.039 | 1/16 |
| 6.35 | 0.250 | 1/4 |
| 12.7 | 0.500 | 1/2 |
| 19 | 0.748 | 3/4 |
| 25.4 | 1.000 | 1 |
| 38.1 | 1.500 | 1 1/2 |
| 50.8 | 2.000 | 2 |
| 76.2 | 3.000 | 3 |
| 101.6 | 4.000 | 4 |
Convert millimeters to inches with decimals and fractions for woodworking and engineering.
| Size | Pilot | Clear |
|---|---|---|
| #4 | 1/16" | 9/64" |
| #6 | 5/64" | 11/64" |
| #8 | 3/32" | 13/64" |
| #10 | 7/64" | 1/4" |
| #12 | 1/8" | 17/64" |
| 1/4" | - | F |
| 5/16" | - | P |
| 3/8" | - | W |
| M4 | 2.5mm | 4.5mm |
| M6 | 3.5mm | 6.6mm |
Identify screw sizes, thread pitches, and head types for woodworking and repairs.