Spanner Size Chart (Metric-Imperial Equivalents)
For your convenience, we’ve compiled a simplified chart of which spanner to use for each size of bolt or nut.
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Are spanners and wrenches the same?
They essentially have the same purpose: to tighten and loosen nuts and bolts. Nevertheless, they have distinct characteristics designed for specific use cases.
Put simply:
- Spanners have slimmer, fixed-sized heads that are designed to drive nuts and bolts of specific sizes.
- Wrenches have a thicker “head" with an adjustable/movable lower “jaw” and are designed to drive nuts and bolts of a range of sizes. Being adjustable, you can virtually use them on any bolt the head and jaw can clamp onto.
Shop for spanners and wrenches.
Metric vs Imperial equivalents
Refer to this table when referencing which spanner size to use for your bolt, nut or screw with a hexagonal head.
METRIC | IMPERIAL UNC/UNF | ||||||
Spanner Size (mm) | Spanner Size (inches) | ||||||
Metric threads | Alternative sizing | Class 4.6/8.8 | Structural | Stainless | SAE | Decimal Inches | Grade 5/8 AF |
AS 1111 | AS 1252 | DIN 931 / 933 / 934 | AS 2465 | ||||
M 1.6 | --- | 3.20 | --- | 3.20 | --- | --- | --- |
M 2.0 | --- | 4.00 | --- | 4.00 | --- | --- | --- |
M 2.5 | --- | 5.00 | --- | 5.00 | --- | --- | --- |
M 3.0 | --- | 5.50 | --- | 5.50 | --- | --- | --- |
--- | 3.18 | --- | --- | --- | 1/8 | 0.125 | --- |
M 4.0 | --- | 7.00 | --- | 7.00 | 5/32 | 0.156 | --- |
--- | 4.76 | --- | --- | --- | 3/16 | 0.188 | --- |
M 5.0 | --- | 8.00 | --- | 8.00 | 3/16 | 0.188 | --- |
--- | 5.56 | --- | --- | --- | 7/32 | 0.218 | --- |
M 6.0 | 6.35 | 10.00 | --- | 10.00 | 1/4 | 0.250 | 7/16 |
M 7.0 | --- | 11.00 | --- | 11.00 | --- | 0.267 | --- |
--- | 7.14 | --- | --- | --- | 9/32 | 0.281 | --- |
M 8.0 | --- | 13.00 | --- | 13.00 | 5/16 | 0.313 | 1/2 |
--- | --- | --- | --- | --- | 11/32 | 0.343 | --- |
M 9.0 | 9.50 | --- | --- | --- | 3/8 | 0.375 | 9/16 |
M 10.0 | --- | 16.00 | --- | 17.00 | 3/8 | 0.375 | 9/16 |
M 11.0 | --- | --- | --- | --- | 7/16 | 0.438 | 5/8 |
M 12.0 | --- | 18.00 | 21.00 | 19.00 | 1/2 | 0.500 | 3/4 |
--- | 12.70 | --- | --- | --- | 1/2 | 0.500 | 3/4 |
M 13.0 | --- | --- | --- | --- | 1/2 | 0.500 | 3/4 |
M 14.0 | 14.30 | 21.00 | --- | 22.00 | 9/16 | 0.563 | 13/16 |
M 15.0 | --- | --- | --- | --- | 9/16 | 0.563 | 13/16 |
M 16.0 | --- | 24.00 | 27.00 | 24.00 | 5/8 | 0.625 | 15/16 |
M 17.0 | --- | --- | --- | --- | 21/32 | 0.656 | --- |
--- | 17.50 | --- | --- | --- | 11/16 | 0.688 | --- |
M 18.0 | --- | 27.00 | --- | 27.00 | 11/16 | 0.688 | --- |
M 19.0 | --- | --- | --- | --- | 3/4 | 0.750 | 1-1/8 |
M 20.0 | --- | 30.00 | 32.00 | 30.00 | 3/4 | 0.750 | 1-1/8 |
--- | 20.64 | --- | --- | --- | 13/16 | 0.813 | --- |
M 21.0 | --- | --- | --- | --- | --- | 0.827 | --- |
M 22.0 | --- | 34.00 | 36.00 | 32.00 | 7/8 | 0.875 | 1-5/16 |
M 23.0 | --- | --- | --- | --- | 29/32 | 0.906 | --- |
M 24.0 | --- | 36.00 | 41.00 | 36.00 | 15/16 | 0.938 | 1-1/2 |
M 25.0 | --- | 36.00 | 41.00 | 36.00 | 1 | 1.000 | 1-1/2 |
M 26.0 | --- | --- | --- | --- | 1-1/16 | 1.0625 | --- |
M 27.0 | --- | 41.00 | 46.00 | 41.00 | 1-1/8 | 1.125 | 1-11/16 |
M 30.0 | --- | --- | --- | --- | 1-3/16 | 1.188 | --- |
M 31.0 | 31.75 | 46.00 | 50.00 | 46.00 | 1-1/4 | 1.250 | 1-7/8 |
M 32.0 | --- | 46.00 | 50.00 | 46.00 | 1-1/4 | 1.250 | 1-7/8 |
M 33.0 | 34.00 | 50.00 | --- | 50.00 | 1-3/8 | 1.375 | 2-1/16 |
--- | 35.00 | --- | --- | --- | 1-3/8 | 1.375 | 2-1/16 |
M 36.0 | 38.00 | 55.00 | 60.00 | 55.00 | 1-1/2 | 1.500 | 2-1/4 |
M 39.0 | 39.69 | 60.00 | --- | 60.00 | 1-9/16 | 1.562 | --- |
--- | 40.00 | --- | --- | --- | 1-9/16 | 1.562 | --- |
--- | 41.00 | --- | --- | --- | 1-5/8 | 1.625 | --- |
M 42.0 | 42.86 | 65.00 | --- | 65.00 | 1-11/16 | 1.688 | --- |
M 45.0 | --- | 70.00 | --- | 70.00 | 1-3/4 | 1.75 | 2-5/8 |
M 48.0 | --- | 75.00 | --- | 75.00 | --- | 1.88 | --- |
M 50.0 | --- | --- | --- | --- | 2 | 2.000 | --- |
M 52.0 | --- | 80 | --- | 80 | 2 | 2.000 | 3 |
M 54.0 | --- | --- | --- | --- | 2-1/8 | 2.125 | --- |
M 56.0 | 57.00 | 85 | --- | 85 | 2-1/4 | 2.250 | 3-3/8 |
M 60.0 | --- | 90 | --- | 90 | 2-3/8 | 2.375 | --- |
--- | 63.50 | 95 | --- | 95 | 2-1/2 | 2.500 | 3-3/4 |
M 64.0 | --- | 95 | --- | 95 | 2-1/2 | 2.500 | 3-3/4 |
M 68.0 | --- | 100 | --- | 100 | --- | --- | --- |
M 72.0 | --- | 105 | --- | 105 | 2-3/4 | --- | 4-1/8 |
M 76.0 | --- | 110 | --- | 110 | --- | --- | --- |
M 80.0 | --- | 115 | --- | 115 | 3 | 3.000 | 4-1/2 |
M 85.0 | --- | 120 | --- | 120 | --- | --- | --- |
M 90.0 | --- | 130 | --- | 130 | --- | --- | --- |
M 95.0 | --- | 135 | --- | 135 | --- | --- | --- |
M 100.0 | --- | 145 | --- | 145 | --- | --- | --- |
M 105.0 | --- | 150 | --- | 150 | --- | --- | --- |
M 110.0 | --- | 155 | --- | 155 | --- | --- | --- |
Table values compiled from:
- Hobson Spanner Selection Chart
- Engineering Toolbox: Wrench Spanner Inches vs MM
- Hand Tools Essentials
- Garage Sanctum
Table labels:
- AS: Australian Standard
- DIN: Deutsches Institut für Normung (German Standard)
- SAE: Society of Automotive Engineers (American Standard originally established for the automotive industry)
- AF: Across Flats
- UNC: Unified National Coarse
- UNF: Unified National Fine
Notes:
- Not all metric fasteners have imperial equivalents, and vice versa.
- Some metric values are close enough to essentially have the same imperial counterpart. In this case, you can use the same spanner size on them.
AIMS' Note on Safe Use of Hand Tools
- Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place.
- Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer.
- Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first.
- PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection.
- Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use.