M27 Bolt & Screw Dimensions: Diameter & Head Size

M27 screw or bolt dimensions and sizes are heavy-duty fasteners primarily found in large-scale structural steel foundations, heavy maritime equipment, mining machinery, and industrial turbine housings. This size has a 27.00mm nominal major diameter and is available in M27 x 3.0 for the coarse series and M27 x 2.0 for the fine series, where 3.0 and 2.0 represent the thread pitch in millimeters. This reference chart follows respective DIN and ISO standards for each head style and DIN 13-1 (coarse), DIN 13-21 (fine), and ISO 68-1 standards for thread dimensions to ensure global compatibility.

Disclaimer: Actual dimensions and tolerances may vary slightly depending on head style (e.g., Hex Head, Heavy Hex, Anchor Bolts), manufacturer, or material grade — always verify with the official product datasheet before use.

Thread diagram for bolt and screw depicting the major diameter, minor diameter, pitch diameter, and thread pitch
Hex head diagram
Cap head diagram
Low-cap head diagram
Button head diagram
Flat head diagram
Pan head diagram
M27 x 3.0 Screw & Bolt – DIN 13-1/ISO 68-1
Dimension Size (mm)
Min Max
Major Diameter 26.577 26.952
Pitch Diameter 24.803 25.003
Minor Diameter 22.955 23.704
Thread Pitch 3.0
Major Diameter 26.577 26.952
Pitch Diameter 24.878 25.003
Minor Diameter 23.03 23.704
Thread Pitch 3.0
M27 x 2.0 Screw & Bolt – DIN 13-21/ISO 68-1
Dimension Size (mm)
Min Max
Major Diameter 26.682 26.962
Pitch Diameter 25.493 25.663
Minor Diameter 24.261 24.797
Thread Pitch 2.0
Major Diameter 26.682 26.962
Pitch Diameter 25.557 25.663
Minor Diameter 24.325 24.797
Thread Pitch 2.0
M27 x 1.5 Screw & Bolt – DIN 13-21/ISO 68-1
Dimension Size (mm)
Min Max
Major Diameter 26.732 26.968
Pitch Diameter 25.844 25.994
Minor Diameter 24.92 25.344
Thread Pitch 1.5
Major Diameter 26.732 26.968
Pitch Diameter 25.899 25.994
Minor Diameter 24.975 25.344
Thread Pitch 1.5
M27 x 1.0 Screw & Bolt – DIN 13-21/ISO 68-1
Dimension Size (mm)
Min Max
Major Diameter 26.794 26.974
Pitch Diameter 26.199 26.324
Minor Diameter 25.583 25.891
Thread Pitch 1.0
Major Diameter 26.794 26.974
Pitch Diameter 26.244 26.324
Minor Diameter 25.628 25.891
Thread Pitch 1.0
  • Major Diameter – The largest diameter of the external thread, measured crest to crest. This defines the nominal size (e.g., M12 which is 12 mm of nominal major diameter).
  • Pitch Diameter – The diameter of an imaginary cylinder where the thread thickness equals the space between threads. This is the critical dimension for thread fit (Tolerance classes 2A/3A for Imperial; 6g/4g6g for Metric).
  • Minor Diameter – The smallest diameter of the external thread, measured root to root. This represents the core strength of the fastener and is the theoretical maximum diameter of the tap drill.
  • Thread Pitch – The distance from a point on one thread to the corresponding point on the next.
Hex Head – DIN 933/ISO 4017
Dimension Size (mm)
MinMax
Width Across Flats 40 41
Width Across Corners 45.2 Not specified
Head Height 16.65 17.35
Metric to Inch Converter
Enter mm to convert to inches
Previous & Next Size Chart
← M24
→ M30

← Choose Another Size

Frequently Asked Questions

What is the tap drill size for M27 screws or bolts?

For metric fasteners, the recommended tap drill size can be calculated using this formula: Major Diameter – Thread Pitch. For an M27 x 3.0 (Coarse), the recommended tap drill is 24.00mm. For an M27 x 2.0 (Fine), the recommended drill size is 25.00mm.

What clearance hole size is needed for an M27 screw or bolt?

For an M27 fastener, a 28.00mm drill bit is utilized for a Close Fit, a 30.00mm bit is used for a Normal Fit, and a 32.00mm bit is recommended for a Loose Fit. A Normal Fit is the industry standard to ensure the bolt shank passes through the assembly without binding while maintaining structural alignment.

What is the equivalent size for M27 in inch (imperial)?

For size M27, the nearest inch (imperial) match is 1-1/16". This particular size has a maximum major diameter of 26.988 mm (1.0625 inch), which means the measurement offset is only about 0.013 mm (0.00053 inch).

While these diameters are nearly identical, metric and imperial fasteners are not interchangeable. They utilize fundamentally different thread systems: Imperial fasteners are measured by Threads Per Inch (TPI), whereas metric fasteners use Thread Pitch. Mixing metric and imperial hardware is strongly discouraged, as it can lead to damaged components, reduced load-bearing capacity, and catastrophic mechanical failure.

What is the difference between a bolt and a screw?

The difference is based on the intent of the fastener’s use; If the primary intent is for the fastener to pass through an unthreaded hole and be assembled with a nut, it is a Bolt. In this application, you usually hold the head and turn the nut to apply tension. But if the primary intent is for the fastener to be installed into a threaded (tapped) hole, it is a Screw. In this application, the connection is tightened by turning the head of the fastener itself.