Nut Size Chart: Metric and Imperial Hex Nut Dimensions Table (Free PDF)

The table list the thread sizes in the first column; find your size there, then read across the row. The value in the third column (max) is called “across flats” which is nominal wrench size. So an M10 nut require a 16 mm socket or spanner.

Find your thread size in the first column, then read across to find the pitch. It’s the coarse thread pitch, which is what ISO 4032 nuts is tapped to. That means an M12 nut will mate to an M12 x 1.75 bolt but won’t mate to a fine thread M12 x 1.5. Everything is in millimetres. These are all for style 1 regular nuts based off ISO 4032, product grades A and B.

s is the measurement across flats. This is face to face measurement across the hexagon. All wrench charts are based on this dimension. Nominal Size is the max value. The manufacturing tolerance floor is the min value of the across flats measurement.

The across corners measurement is e. When checking clearances next to a wall, in a recessed socket, or counterbore, you use this measurement which are approximately 1.155 times the across flats size.

Thickness m. The overall height of the nut include the washer face if it has a washer. For regular style 1, these nuts runs around 0.9 times the thread diameter.

The old-style DIN 934 head sizes can cause confusion. For example, older DIN 934 nuts is 17 mm across flats for M10, 19 mm for M12, 22 mm for M14, and 32 mm for M22. The corresponding ISO 4032 sizes is 16, 18, 21, and 34 mm. They both is out there and circulating.

An M10 nut that rattles around on your 16 mm spanner is likely to be DIN (not a warn nut) for sure. All of the other will match up between standards.

Note: Structural nuts aren't included in this table. These nuts has bigger across flats for high strength structural assemblies to either AS 1252 or EN 14399. In these systems, the smaller nuts gets bigger heads, e.g., from 21 mm on M12 and 46 mm on M30.

The type 2 (ISO 4033) nuts are approximately 10 percent taller then the corresponding type 1 (listed above). The thin, flange and nyloc patterns each has its own table later on the page.

Use callipers and read off the across flats dimension of an unfamiliar nut then compare that to this column. Don't attempt to judge by eye. It would of worked for separating pairs like M8/M10 (13 vs 16 mm), M12/M14 (18 vs 21 mm). Because a nut's bore measure larger than the bolt's nominal diameter, you could be misled if only judging thread size.

The first column is the bolt diameter. The second is the nominal width across flats F basic, which is the fraction and decimal equivalent number stamped on your wrench. A 3/4 in wrench are used for a 1/2 in hex nut.

F min is the smallest a conforming nut may measure. Column four is G max. It is the width from corner to corner so you can do clearance checks. Columns five and six are H thickness and that’s the height of the standard hex nut. Columns seven and eight are H1, the height of the corresponding half or jam nut. All measurements are in inches per ASME B18.2.2.

Below 5/8 in., it's rule of thumb again: Add 3/16 in to the diameter to get the wrench size (column F). From 5/8 in. up, multiply the diameter by 1.5 (also F column). That's what makes imperial wrench sizes seem so odd compared to their metric counterparts; this change occur right here.

Here, the full size hex pattern starts at 1/4, 5/16 and 3/8 in nuts. For the same thread series on small machine screws there's also an ASME B18.6.3 nut series that features smaller heads. Before ordering a wrench, double-check what pattern is yours.

Are you looking for a thin nut for a tight space? No, that’s a jam nut and its purpose is to lock. First you run the jam nut down. Then you tighten the full nut over it. That’s when the two nut oppose each other and load the threads. This resists vibration.

If you do it the opposite way round with the full nut first then the assembly have lost much of its locking effect. The jam nut only has reduced thread engagement. It must never ever be used alone on a joint which see the full rated load of the bolt.

The first near miss trap is that two nuts that look alike in your hand is 9/16 in and 5/8 in. Yet they require different wrenches (7/8 and 15/16). If the wrench is loose on the flat sides, use the next size down before forcing it.

Second, watch for metric near misses. A 19 mm DIN M12 nut is often turned by a 3/4 in wrench (19.05 mm). But a 24 mm M16 nut (0.945 in) is sloppy enough to round corners when torqued with a 15/16 wrench. Compare metric sizes before using mixed tools by using the decimal values from this table.

The plain finished hex pattern is shown in this table. It is for general purpose and SAE J429 bolts.

For structural bolted applications like ASTM A325 and A490 (now F3125) you need the heavier hex pattern, as shown in the following table. The hex pattern thicken and widens for each size.

Hex goes up to 4 inches above 1 1/2 in. At this point, plain hex stock becomes less common. Most will push you into heavy hex at this point anyway.

In the conventional sequence, you will see the same reading order as standard imperial table. The first number is the nominal width across flats and the decimal value. Second is called the tolerance floor which is F min. Third is the across corners range for clearance, G. Fourth is the nut thickness range, H.

Heavy hex is easy: 1.5 times the bolt diameter + 1/8 in. This equal the distance across the flats. The heavy hex nut is the same size as next larger wrench in a standard set. This is one step larger than equivalent plain hex nut with the same thread size.

Why Do Heavy Hex Nuts Exist?

They have more steel around the thread, which increase its resistance to being stripped. They’re required for structural bolting such as ASTM F3125 grades A325 and A490. According to the grade pairing table below, you’ll want to use a nut to A563 or A194.

B7 stud bolts are standard on ASME B16.5 flanges. Beyond 1 1/2 in., the plain pattern drop from distribution so this becomes the default.

The thickness provides increased thread engagement. It’s about equivalent to one full bolt diameter vs. it is 7/8 of it. This aids hot dip galvanized assemblies where the nut is tapped oversize.

The most frequent error with this table involve wrenches. On 1/2 in structural bolt you use a 7/8 in wrench on the nut end. Plain hex says 3/4 in for the table but it’s not right for this task.

For flange work both the bolt head and the nut are heavy hex. That means one size of wrench fit both ends. For structural work the bolt head is heavy hex as well.

BUT, the tension control (TC) bolts has a round head. The bolt is never driven except from the nut.

The thickness of these imperial heavy jam nuts. Don't rely on this table to size those. Those will be thinner nuts. Eg. On a 1/2 in nut, the maximum is 0.317 in. This does not apply to grade 2H nuts (eg A194) cut on an 8UN pitch greater than 1 in.

Same dimensions as here, just don't assume that's the same thread series as UNC. If you're replacing a heavy hex nut on some old piece of machinery, get out the pitch gauge and measure the thread first.

The columns here read as in the ISO 4032 table above, just read them as they appear. The wrench size is s. Next is e. Lastly is the thickness.

Everything is in millimetres. ISO 4035 thin nuts has the same across corners and across flats dimensions as ordinary ISO 4032 nuts. The only difference is the thickness. It goes down to roughly one-half the diameter of the threads. They is also known as lock nuts, half nuts, or jam nuts.

There are two valid applications. These include adjustment collars, linkage ends, and space-starved assembly where a normal nut won’t fit and the load is modest.

Second use is where you have a jam nut (locking pair) Tighten the thin one first per ISO 898-2 to the joint. Next add the regular nut. The pair grips the thread flank in opposing directions.

That is where the standard addresses critical safety. Reduced capacity applies to thin nuts. Thin nuts aren’t made to withstand stripping of thread.

The full proof load of a 10.9 or 8.8 bolt should of never be carried by a class 05 or 04 thin nut alone. If your load is real and your height matter, you must account for the reduced capacity. In that case, you use a class 05 thin nut. Or you redesign the assembly for a full nut.

These nuts suffer from the exact same DIN legacy trap as do full nuts. What you find in the wild is a mix of DIN 439 (now DIN 439-2) and EN ISO 4035 stock.

DIN 439 used 17, 19, 22, and 32 mm wrench sizes on M10, M12, M14, and M22. Those match up to M10, M12, M14, and M22 bolt sizes. Both generations has the same height. To determine which generation a loose thin nut is from, you can only use its wrench size.

Don't get confused between ISO 4035, and ISO 4036. The latter is an unchamfered pressed thin nut. The tolerances are a bit different; it has DIN 936 heritage, product grade B. You can commonly find them in a cheap assortment from a hardware store.

For imperial jam nuts you use the H1 columns of the imperial table above. Don't convert these metric heights.

So you locate the cross flats measurement, the thread size, and you see the two columns of height which explain how the nut is built. Total height is all stacked up including the nylon collar. That’s what you measure for clearance and for how much the bolt stick out.

And the wrenching height is just the height of the steel hex down from the collar. That’s what takes the load. That’s where you put the socket. Above that, it’s a little bit thinner in the collared domed zone, don't get your open end wrench wrapped around there when you’re torquing.

Why is the bolt longer than a plain nut? It is because of the height column. An M10 nyloc is 10 mm high. A plain M10 nut is 8.4 mm high.

Then there’s the fact that you have to get the bolt all the way through the insert. For the lock to work, you’ve got to have at least one to two good threads clean out beyond the nylon. If your bolt stops flush with the interior of the collar, it’s unlocked.

The above information pertains to the low profile prevailing torque family which contains both DIN 985 and the new standard, ISO 10511. These thin nuts is classified by rules in property class 05. Nuts typically found here would be those identified only as a stop nut or nyloc hardware.

High nuts follow standards such as DIN 982 or ISO 7040. The height of these nuts will be roughly 10 to 20 percent taller. For maximum load capacity of the bolt they has full class 8 or 10 height. If you need the nut to handle the full proof load of the bolt, you should of specify the high type.

Three rules of thumb govern use. Because the collar relies on friction to hold, (1) reuses are limited, as each use wears off some of the insert’s holding power; (2) apply a new nut each time on critical joints; and (3) the temperature range is approximately, -40 to +120 degrees C for standard polyamide inserts.

Beyond that, use all metal prevailing torque nuts such as ISO 7042 or DIN 980. Running a die or tap through the insert destroys it, too. Similarly, using an impact gun to spin on the nut from the collar side damage the insert.

In this case, there’s a double version of the wrench size trap. Already, there’s the DIN versus ISO across flats, with M10, M12, M14 and M22 size.

Commonly, fine threads (like M10 x 1.25) on Japanese cars are automotive nylon lock nuts. Fine pitch versions uses the same wrench sizes and height. They’re covered by DIN 985, which also covers coarse pitch versions. But again, make sure it’s the right exact thread.

Across flats s Look at two diameters that define flange nuts. The minimum bearing diameter are the guaranteed flat contact circle. It spreads the clamping load.

Flange dia dc max is the outer diameter of the integral washer face. It need to fit inside a recess or sit against any adjacent hardware. Check the wrench size.

The maximum height m is the total height including the flange. It is comfortabley equal to the thread diameter at every size.

The primary trap on this table is M10. On M10, it is a flange nut per DIN 6923, which require a 15 mm wrench. It is not a plain ISO nut (16 mm) or a stock DIN 934 (17 mm). That's because the flange bear the load and the hexagon corners doesn't need to do so.

For the other sizes, the wrench stay the same as what you're used to, except double-check your socket. For practical purposes, the dimensions match its ISO counterpart ISO 4161. Small flange nuts per JIS B 1190 goes smaller yet (again): common on Japanese vehicle.

Instead of a separate flat washer, it has a flange. This flange distribute force evenly across the oversized holes, slots, or painted surfaces without adding another piece that can fall out. They come in a version with serrated sides which lock on the mating surface like a ratchet.

On painted steel or bare surfaces, use serrated ones if you don't mind the witness marks. On finished surfaces or soft alloy use plain faced ones.

Typically, DIN 6923 flange nuts are shipped property class 8 and 10. Use them like plain nuts and match bolts precisely by the grades shown in the chart.

The table is for standard nuts only; it does not apply to large flange weld nuts or serrated flange nuts sold under IFI 145 (patterns vary).

Torque values for flange nuts will be a little above those of a comparable plain nut because the flange inhibits tipping. If your joint concern you, go by torque table from the fastener maker.

The metric columns say: Fit the nut from the second column to the bolt you looked up in the first column. The third column shows any nut that is an acceptable upgrade (never a downgrade), so anything there is OK.

The logic for the metric rows are spelled out in ISO 898-2. This say that the single digit nut class equals the number before the point of the highest bolt class it may carry. So 8.8 bolts gets class 8 nuts, 10.9 gets class 10, etc. And 12.9 gets class 12.

That's why you see that digit stamped on a metric nut, or a code on small nuts that looks like a clock face. On imperial A563 grades, such as C, D, and DH, they is marked with letters. SAE J995 grade 5 and 8 nuts is marked with dashes around their circumference.

Secondly, matching is important, as a weak nut is no match for a strong bolt. It will strip its threads long before the bolt fails. Torque wrenches don’t measure thread stripping, which is a slow, hidden form of failure.

That’s why design codes mandate that the nut proof load must be at least the bolt's minimum ultimate tensile strength. The response to “where’d the (class 10) nut go?” is always, “Put in a (class 12) nut.” You should of not pull a class 8 nut from the same drawer.

Take care with the structural rows. Heavy hex nuts from the heavy hex table above are required for A325 and A490 bolts. An A563 A plain hex nut on a structural bolt is not just a bad choice, it’s a code violation.

Pairing changes with galvanized assemblies. To clear the zinc, the nut is tapped oversize, cutting thread engagement. Thus, the harder DH grade are required. Because DH is scarce above 3/4 in., A194 2H is a common substitute. Hot dip galvanizing A490 bolts is never allowed, due to the risk of hydrogen embrittlement.

There are two additional traps. For the same reason as oversize tapping, hot dip galvanized metric nuts loses stripping strength. Thus galvanized 8.8 bolting use proof tested and manufactured oversize class 8 nuts. Galvanized bolt plus plain tapped nut simply won't assemble.

And finally, stainless A2-70 or A4-70 is its own system. Pair stainless bolts of the same grade with stainless nuts. Don’t map it onto these carbon steel classes in the table.

This section covers carbon and alloy steel.

These are for regular bolts. These are not for high temperature service. Use matching ASTM A194 Grades to B7, B8, and B16 studs from the same standard.

This is not for property class 04 and 05 thin nuts with primary load. Those is described on the thin nut table above. These are not for EN 14399 preloaded structural assemblies. In these instances, you have lot-tested, matched bolts and nut in a set.