Standard Inch Flat Washer Size Chart

Washer Size vs Bolt Size

Washer Dimensions Explained

ID = inside diameter. OD = outside diameter. T = thickness. These three abbreviations are used consistently in every table on this page.

A washer distributes bearing load, protects a surface, bridges an oversized or slotted hole, provides a hardened bearing surface, accommodates geometry, or supports a locking system where specifically designed for that purpose. Not every washer prevents loosening; that function depends on the specific washer style and design.

Nominal washer size refers to the compatible bolt diameter. A 3/4-in. washer means it is intended for a 3/4-in. fastener. It does not mean a 3/4-in. inside diameter, a 3/4-in. outside diameter, or a 3/4-in. thickness. For ASTM F436, a nominal 3/4-in. washer uses a 13/16-in. inside diameter, not exactly 3/4 in.

Additional features on some washers include a chamfer or bevel where applicable, and a defined bearing face.

Washer ID must be larger than the nominal bolt diameter so the washer slides freely onto the bolt shank, accounting for manufacturing tolerances on both parts.

This is one of the strongest comparison tables on the page: four washers fitting the same nominal bolt can have four different outside diameters depending on pattern.

ASTM F436 standard-thickness washers are typically in the 0.097 to 0.177 in. range depending on size, while extra-thick F436 washers run roughly 0.305 to 0.375 in. for sizes up through 1-1/2 in.

SAE pattern generally has a smaller OD and a more compact bearing footprint, while USS pattern generally has a larger OD and greater bearing area. SAE and USS are washer patterns, not bolt grades, and should not be confused with SAE bolt-strength grading.

Values are cross-referenced against ASME B18.21.1 Type A narrow-pattern dimensional data.

USS pattern can be useful where larger bearing area, softer material, or larger clearance holes are involved. This does not mean USS is inherently a stronger washer; it simply provides a larger bearing footprint.

For the same nominal bolt size, USS pattern generally has a larger outside diameter than SAE pattern. For example, at 1/2 in., SAE OD is 1.062 in. while USS OD is 1.375 in. At 3/4 in., SAE OD is 1.469 in. while USS OD is 2.000 in. Actual dimensions should always come from the selected standard or product rather than assumed from a general rule.

ASME B18.21.1 covers dimensional requirements for plain washers along with lock-washer families. This includes the standard flat washer, regular series, in the washer patterns and materials or finishes discussed throughout this page. Structural hardened washers are covered separately in the following sections, since ordinary plain washers do not meet ASTM F436 hardness requirements.

ASTM F436/F436M covers hardened washers for general mechanical use, structural applications, and high-strength fastener assemblies. Type 1 is carbon steel; Type 3 is weathering steel.

ASTM F436 includes extra-thick washer dimensions. Extra-thick washers for common 1/2 through 1-1/2-in. sizes run roughly 0.305 to 0.375 in., compared with the standard thickness range of about 0.097 to 0.177 in. Extra-thick washers may be specified for oversized holes, slotted holes, structural connections, or specific AISC/project conditions, but they are not optional substitutes for standard washers everywhere; use the exact thickness called for by the connection specification.

ASTM F436 beveled washers are intended for American Standard beams and channels to compensate for surface slope or nonparallelism, using a 1:6 bevel across nominal sizes from about 1/2 through 1-1/2 in.

Clipped washers are used when the full round washer will not fit or edge clearance is restricted. Minimum edge distance is product and application-specific and should be confirmed against the manufacturer’s published data for the exact clipped washer being used.

Fender washers have a relatively small ID with a much larger OD, providing a broad bearing surface. Applications include sheet metal, thin materials, enlarged holes, and surface protection. Fender washers are not structural equivalents to ASTM F436 hardened washers and should not be substituted for a specified structural washer.

Split, or helical spring-lock, washers use a split geometry with a defined nominal size, ID, OD, and section thickness. This page does not claim spring washers universally prevent loosening under vibration, since that depends on the specific joint and system design.

Washer ID must clear the bolt while the washer still provides enough bearing around the hole. Bolt diameter, hole diameter, washer ID, and washer OD are all related but distinct values, and washer ID should not be assumed to equal the bolt hole diameter in every standard; the exact relationship depends on the applicable specification.

Potential governing issues include washer OD, washer thickness, hardness, slot orientation, and plate washer requirements. This page does not give a one-size-fits-all rule for oversized or slotted holes; use the applicable AISC, RCSC, or project requirements, and keep detailed structural connection design outside the scope of this general reference chart.

ASTM F436 controls chemical composition, Rockwell hardness, dimensions, and thickness. Hardened washers prevent local indentation under high-strength bolt and nut bearing and provide a suitable hardened bearing surface. Ordinary soft washers should not be substituted where F436 is specified.

Common options include carbon steel, stainless steel, weathering steel, zinc plated, hot-dip galvanized, and plain finish. For ASTM F436, Type 1 is carbon steel and Type 3 is weathering steel.

Hot-dip galvanized F436 washers exist and are commonly supplied in both plain black and hot-dip galvanized finishes for circular and beveled styles. Do not mix finishes casually in engineered structural assemblies; the washer coating should be coordinated with the bolt and nut finish specified for that connection.

A washer sits beneath a bolt head, a nut, or sometimes both, so bearing footprint, OD, hardness, and nut type all need checking together. See the Nut Size Chart and Hex Bolt Size Chart for the mating fastener dimensions.

As of the most recent publication, ISO 7089:2000 remains the published current standard for plain washers, normal series, product grade A, though a replacement revision is under development. This chart follows that ISO dimensional data rather than a converted inch table.

This family of standards distinguishes normal, chamfered, small, and large series, demonstrating that metric washers, just like inch washers, are not dimensionally identical simply because they fit the same nominal fastener size.

ASME B18.21.1 covers plain washers, helical spring-lock washers, and tooth-lock washers. The standard includes plain washers from #0 through 3 in., while inclusion in the dimensional standard does not mean every size is commercially stocked.

The current active reference is ASTM F436/F436M-24, which covers hardened washers for nominal fastener diameters from 1/4 through 4 in. and metric M12 through M100. This standard is central to any structural construction application requiring a hardened bearing washer.