Metric bolts are measured in millimeters and are typically denoted by the letter “M” followed by a number, which represents the nominal diameter of the bolt. For example, an M10 bolt has a diameter of 10 millimeters.
If you’re like me and typically measure bolt sizes by the head size (e.g., a 17mm bolt or nut head), it can often get confusing when trying to determine the actual spanner size required for a metric bolt. That’s where our handy Metric Bolt to Spanner Size Conversion Chart comes into play.
Whether you’re ordering new nuts and bolts or simply trying to find the correct replacement from your nuts and bolts storage (mine is usually an old bucket), having a handy chart guide is always a useful tool. It ensures you select the correct size every time.
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Metric Bolt to Spanner Size Conversion Chart –
To help you quickly identify the correct spanner size for different metric bolts, refer to our following conversion chart:
| Metric Bolt Size (Diameter) | Spanner (Wrench) Size |
|---|
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Metric Socket Cap Bolt to Spanner Size and Hex Key Conversion Chart –
| Metric Bolt Size (Diameter) | Spanner (Wrench) Size | Socket Cap Bolt Hex Key Size |
|---|
What Size Spanners For Metric Bolts –
What size spanner for an M5 bolt?
An 8mm spanner is required for an M5 bolt, and a 4mm hex key is needed for an M5 Socket cap bolt.
What size spanner for an M6 bolt?
An M6 bolt requires a 10mm spanner, and an M6 socket cap bolt requires a 5mm hex key.
What size spanner for an M8 bolt?
A 13mm spanner is required for an M8 bolt, and a 6mm hex key is needed for an M8 Socket cap bolt.
What size spanner for an M10 bolt?
An M10 bolt requires a 17mm spanner, and an M10 socket cap bolt requires an 8mm hex key.
What size spanner for an M12 bolt?
A 19mm spanner is required for an M12 bolt, and a 10mm hex key is needed for an M12 Socket cap bolt.
What size spanner for an M14 bolt?
A 22mm spanner is required for an M14 bolt, and a 12mm hex key is needed for an M14 Socket cap bolt.
What size spanner for an M16 bolt?
A 24mm spanner is required for an M16 bolt, and a 14mm hex key is needed for an M16 Socket cap bolt.
What size spanner for an M18 bolt?
A 27mm spanner is required for an M18 bolt, and a 14mm hex key is needed for an M18 Socket cap bolt.
What size spanner for an M20 bolt?
A 30mm spanner is required for an M20 bolt, and a 17mm hex key is needed for an M20 Socket cap bolt.
What size spanner for an M22 bolt?
A 32mm spanner is required for an M22 bolt, and a 17mm hex key is needed for an M22 Socket cap bolt.
What size spanner for an M24 bolt?
A 36mm spanner is required for an M24 bolt, and a 19mm hex key is needed for an M24 Socket cap bolt.
What size spanner for an M27 bolt?
A 41mm spanner is required for an M27 bolt, and a 19mm hex key is needed for an M27 Socket cap bolt.
What size spanner for an M30 bolt?
A 46mm spanner is required for an M30 bolt, and a 22mm hex key is needed for an M30 Socket cap bolt.
What size spanner for an M33 bolt?
A 50mm spanner is required for an M33 bolt, and a 22mm hex key is needed for an M33 Socket cap bolt.
What size spanner for an M36 bolt?
A 55mm spanner is required for an M36 bolt, and a 24mm hex key is needed for an M36 Socket cap bolt.
What size spanner for an M39 bolt?
A 60mm spanner is required for an M39 bolt, and a 24mm hex key is needed for an M39 Socket cap bolt.
What size spanner for an M42 bolt?
A 65mm spanner is required for an M42 bolt, and a 27mm hex key is needed for an M42 Socket cap bolt.
What size spanner for an M45 bolt?
A 70mm spanner is required for an M45 bolt, and a 27mm hex key is needed for an M45 Socket cap bolt.
What size spanner for an M48 bolt?
A 75mm spanner is required for an M48 bolt, and a 30mm hex key is needed for an M48 Socket cap bolt.