Standard Inch Hex Nut Size Chart

Standard Hex vs Heavy-Hex Quick Chart

Heavy-hex nuts are 1/8 in. larger across flats than standard hex nuts of the same nominal size across this common range, and they are also thicker.

A nut is an internally threaded fastener designed to mate with a bolt, threaded rod, stud, or machine screw with matching nominal diameter, thread pitch, thread form and class, and compatible material or grade where required.

1/2-13 UNC means a nominal thread diameter of 1/2 in. with 13 threads per inch, a coarse Unified thread. 1/2-20 UNF means the same nominal diameter but 20 threads per inch, a fine Unified thread. The mating bolt must match both diameter and pitch exactly.

Additional features include the bearing face, chamfer, and internal thread relief at the bearing surface.

ASME B18.2.2-2022 is the governing dimensional source for these values. A 1-in. finished hex nut has a 1-1/2-in. basic width across flats and a basic thickness of 55/64 in.

This table connects directly to the Socket Size Chart and the Hex Bolt Size Chart. The socket matches the width across flats, not the nominal thread diameter.

This distinction is particularly useful in CAD, connection detailing, and tight recesses where the full diagonal envelope of the nut matters more than the flat-to-flat wrenching dimension.

Do not infer strength from thickness alone; thickness affects thread engagement and proof-load behavior, but mechanical grade is a separate specification.

Heavy-hex nuts are wider across flats, wider across corners, and slightly thicker than standard finished hex nuts at the same nominal diameter.

Larger structural sizes continue well beyond ordinary finished-hex stock ranges, extending up to 2-3/4 in. and beyond depending on grade and manufacturer.

Do not assume a jam nut has the same proof-load capability as a regular nut of the same thread size, since its reduced thickness affects thread engagement.

Lock Nuts

Common lock-nut families include prevailing-torque distorted-thread nuts, nylon insert nuts, all-metal lock nuts, and serrated flange lock nuts. A prevailing-torque locknut resists rotation through thread distortion. Locking style does not automatically change nominal thread size, but nut height and external geometry can differ from a standard finished hex nut.

Hex Flange Nuts

Flange nuts have an integral flange at the base that distributes clamping load over a wider bearing area. Relevant dimensions include thread size, across flats, nut height, flange diameter, and flange thickness. ASME B18.2.2-2022 explicitly includes hex flange nuts within its general inch-series nut scope, but flange-nut outer diameter should not be mixed into ordinary hex-nut charts.

Hex Coupling Nuts

Coupling nuts are long nuts used to connect threaded rods, studs, or anchor rods. A 1/2-in. finished-pattern coupling nut has a basic width across flats of 11/16 in. and a nominal length of about 1-3/4 in., which is considerably longer than an ordinary hex nut’s thickness. Do not confuse coupling-nut length with ordinary hex-nut thickness.

Square Nuts

ASME B18.2.2 also covers square nuts, which have a square external shape, different bearing geometry in some applications, and different wrenching behavior than hex nuts. This is a supporting note rather than a focus of this hex-nut-centered page.

For the complete UNC dimensional reference including tap drill sizes, see the UNC Thread Chart.

For the complete UNF dimensional reference, see the UNF Thread Chart.

A 1/2-13 nut will not correctly mate with a 1/2-20 bolt, even though both share the same nominal 1/2-in. diameter. The thread series must match exactly.

Internal Unified thread classes such as 1B, 2B, and 3B describe allowance and tolerance grade for nut threads. This page explains fit and compatibility at a practical level, while the Thread Pitch Chart and related thread charts own the deeper thread dimensional data.

A compatible nut must match nominal diameter, thread pitch, thread system, required grade or material, and coating condition where relevant. The compatibility logic is: diameter, plus pitch, plus thread system, plus grade and finish compatibility, all four together, not diameter alone.

Nut grade does not inherently determine external dimensions. An ASTM A563 Grade DH heavy-hex nut and an ASTM A194 Grade 2H heavy-hex nut can use the same ASME B18.2.2 heavy-hex dimensions even though their mechanical grades differ. Nut dimensions and nut mechanical grade are separate specifications. For grade and marking details, see the Bolt Grade Chart.

These grades are available in hex or heavy-hex styles depending on grade, bolt pairing, size, and finish. This page focuses on compatibility and style rather than reproducing a complete mechanical-strength table, since that data belongs on the dedicated Bolt Grade Chart.

ASTM A194 nuts are commonly used in higher-temperature, high-pressure, and structural applications depending on grade, with ASTM A194 defaulting to the heavy-hex series unless otherwise specified. Grade 2H is a common example, explicitly permitted by ASTM F3125 as a substitute for ASTM A563 Grade DH on structural bolts. This page keeps focus on compatibility and style rather than becoming a full A194 mechanical-property reference.

ASTM F3125 Type 1 A325 and A490 structural bolts are commonly paired with specified A563 heavy-hex grades, such as C, C3, D, or DH, depending on bolt type and plain versus galvanized finish, and ASTM A194 Grade 2H heavy-hex nuts are explicitly permitted as a substitute for A563 Grade DH on these bolts. Structural bolt-nut compatibility is not based only on matching diameter and thread; grade and coating matter and must be verified against the applicable specification.

Hot-dip galvanizing adds coating thickness to threaded fasteners. Galvanized nuts are tapped oversize to accommodate the coating on mating galvanized bolts, with specific oversize allowances codified in ASTM A563. Do not pair a galvanized bolt with an arbitrary standard-tapped nut unless the assembly or specification permits it; using a non-oversize-tapped nut on a galvanized bolt can prevent proper thread engagement or damage the coating.

Manufacturer weight tables also cover finished jam, heavy-hex jam, square, and heavy square nuts. These figures help with estimating, shipping, and inventory planning rather than structural design.

ISO 4032 covers hexagon regular nuts (style 1) with metric coarse-thread sizes M5 through M39, product grades A and B. As with sockets, some diameters such as M10 and M12 have a different wrench size under the older DIN 934 standard versus current ISO 4032.

For the complete SAE and metric socket reference, including drive size and 6-point versus 12-point guidance, see the Socket Size Chart.

For deeper thread identification support, see the Thread Identification Chart and the Thread Pitch Chart.

ASME B18.2.2-2022 is the current inch-series dimensional standard, covering hex nuts, heavy hex nuts, square nuts, hex jam nuts, heavy hex jam nuts, hex flange nuts, hex coupling nuts, and machine-screw nuts. ASME states that the tabulated dimensions govern, and it also notes that inclusion in the standard does not imply every listed product is commercially stocked.

ISO 4032:2023 covers hexagon regular nuts (style 1) with metric coarse-thread sizes M5 through M39, in product grades A and B. Metric nut dimensions follow this separate international standard rather than being derived from inch nut dimensions.