🔩 Hex Nut Dimensions Calculator
Check across flats, across corners, socket clearance, thread engagement, and proof load for ISO, UNC, heavy hex, and jam nut layouts.
📌 Preset Nut Sizes
⚙ Calculator Inputs
🎯 Results
📊 Material and Spec Comparison
📑 Series Comparison Grid
ISO Regular
General machine nuts with balanced height and standard wrench proportions. Good default for metric equipment and assemblies with limited envelope growth.
ISO Style 2
Taller and broader pattern for larger diameters or higher clamp demand. Expect more socket room and higher engagement turn count than regular style.
Finished Hex
Common ASME inch pattern for consumer, maintenance, and general fabrication joints. Works well when envelope size matters more than peak clamp margin.
Heavy or Jam
Heavy nuts increase bearing footprint; jam nuts reduce height for locknut stacks. Both need a deliberate engagement check because their geometry shifts fast.
📋 Reference Tables
| Metric size | Pitch | Across flats | Nut height | Across corners |
|---|---|---|---|---|
| M6 | 1.0 mm | 10 mm | 5 mm | 11.55 mm |
| M8 | 1.25 mm | 13 mm | 6.5 mm | 15.01 mm |
| M10 | 1.5 mm | 17 mm | 8 mm | 19.63 mm |
| M12 | 1.75 mm | 19 mm | 10 mm | 21.94 mm |
| M16 | 2.0 mm | 24 mm | 13 mm | 27.71 mm |
| M20 | 2.5 mm | 30 mm | 18 mm | 34.64 mm |
| UNC size | TPI | Across flats | Nut height | Across corners |
|---|---|---|---|---|
| 1/4-20 | 20 | 7/16 in | 7/32 in | 0.505 in |
| 5/16-18 | 18 | 1/2 in | 17/64 in | 0.577 in |
| 3/8-16 | 16 | 9/16 in | 21/64 in | 0.650 in |
| 1/2-13 | 13 | 3/4 in | 7/16 in | 0.866 in |
| 5/8-11 | 11 | 15/16 in | 35/64 in | 1.083 in |
| 3/4-10 | 10 | 1-1/8 in | 41/64 in | 1.299 in |
| Series | Typical height | Socket room | Best use |
|---|---|---|---|
| ISO regular | 0.8d to 1.0d | Standard | Machine builds |
| ISO style 2 | 1.0d to 1.2d | More room | High clamp |
| Finished hex | 0.85d to 0.9d | Compact | General service |
| Heavy hex | 0.9d to 1.0d | Large OD | Structural joints |
| Jam nut | 0.45d to 0.6d | Low stack | Lock pairs |
| Material | Proof strength | Finish trend | Allowance note |
|---|---|---|---|
| Grade 2 steel | 55 ksi | Plain or zinc | 5 to 10% |
| Grade 5 steel | 85 ksi | Zinc or oil | 5 to 10% |
| Grade 8 steel | 120 ksi | Yellow zinc | 10 to 15% |
| Class 10 | 830 MPa | Black oxide | 5 to 10% |
| 304 stainless | 65 ksi | Passivated | 10 to 15% |
| Brass | 30 ksi | Plain brass | 0 to 5% |
💡 Fit Notes
This calculator sizes hex nut wrench clearance, engagement, and proof load from real geometric inputs so you can compare metric and inch nut envelopes before finalizing a hardware stack.
A nut occupies a specific amount of space, and the nut’s geometric envelope dictate the amount of clearance that is required for that nut. Many people may think that a nut is just a cylinder with a hole in the center of the nut, but the nut have complex dimensions that dictate exactly how that nut is to fit within a chassis or other enclosure. In order to determine the exact clearance requirements for a nut within a design, it is first necesary to understand the different dimension of that nut.
The most common measurement of a nut is the across flats dimension of the nut; the across flats dimension measure the distance between the two flat side of the nut. This measurement is used to identify the size of a wrench that a user will use to tighten the nut to the desired specification; however, this is not the widest part of the nut. The widest part of the nut is the across corners dimension of the nut, which measures the distance between the opposite corner of the nut’s hexagon.
How to Measure a Nut and Make It Fit
Because a hexagon have six equilateral triangle within it, the across corners dimension will always be larger then the across flats dimension of the nut. Thus, if someone design a hole or recess in an object, they may find that the nut will not fit if they only use the across flats dimension as a specification of where the nut should fit. Beyond the dimensions of the nut, another factor to consider is the thickness of the coating that may be applied to the nut.
For instance, if someone will powder coat the nut or if it will be galvanized, the thickness of each of these treatments will increase the diameter of the nut. This increased diameter may prevent a socket from being able to slide over the nut to allow the nut to be tightened. Thus, the thickness of any such coatings should of been considered in the design of the object to which the nut is to be attached; otherwise, the nut may not fit within a hole that was drilled in the object.
Another consideration for nuts is the thread engagement of the nut. Thread engagement is used to measure the strength of the nut when it is attached to a bolt. For instance, jam nuts has less thread engagement than standard nuts; jam nuts are thin version of the standard nut.
Additionally, if a nut has less than six turn of thread engagement, it may strip if the bolt is subjected to a heavy load. The number of turns can be calculated by dividing the height of the nut by the pitch of the thread of the bolt; the result will be the number of rotations that the nut will make on the bolt. The material of the nut is another consideration in the design of a nut.
For instance, the material of the nut will impact the proof load of the nut. Proof load is the amount of force that the nut can withstand before it starts to deform. Different material have different proof loads; for instance, Grade 2 carbon steel nuts can be used in designs that exert less force than nuts made of alloy Grade 8 metal or ISO Class 10 nuts.
Additionally, the strength of a nut can be calculated using the tensile stress area of the nut; the tensile stress area of the nut is the theoretical diameter of the bolt that is actualy made of metal that will distribute the load of the nut. These two measurements is not the same; the tensile stress area should not be treated as more same as the diameter of the bolt. Beyond these factors, the specific series of nuts can change the size of the nut.
For instance, heavy hex nuts have a larger bearing surface than finished hex nuts. Thus, if a design use standard hex nuts that are replaced with heavy hex nuts, the nuts may not fit within the designated area of that design. Finally, it is also important to include an allowance in the design for the wrench that will be used to turn the nut; this allowance accounts for the thickness of the wrench and the movement of the hand when tightening the nut.
Thus, providing an allowance for the wrench to fit within the design will ensure that the wrench are able to successfully turn the nut.
