Washer Size Finder
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1/2" SAE flat washer
Commercial SAE-pattern reference dimensions. Verify the governing drawing or specification for tolerances, material and hardness.
SAE and USS Washer Size Chart
Commercial inch-series flat washer reference. Fractional inch values are shown first when a practical fraction applies, followed by decimal inches and millimeters. Nominal size is the mating fastener designation, not the washer hole diameter. Source [1]
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Scroll within this table to view additional columns or rows. The first column identifies each washer size and family.
| #2 SAE | 3/32″0.09375 in · 2.38 mm | 1/4″0.25 in · 6.35 mm | 0.02″0.51 mm |
|---|---|---|---|
| #4 SAE | 1/8″0.125 in · 3.17 mm | 5/16″0.3125 in · 7.94 mm | 0.032″0.81 mm |
| #6 SAE | 5/32″0.15625 in · 3.97 mm | 3/8″0.375 in · 9.52 mm | 0.049″1.24 mm |
| #8 SAE | 3/16″0.1875 in · 4.76 mm | 7/16″0.4375 in · 11.11 mm | 0.049″1.24 mm |
| #10 SAE | 7/32″0.21875 in · 5.56 mm | 1/2″0.5 in · 12.70 mm | 0.049″1.24 mm |
| #12 SAE | 1/4″0.25 in · 6.35 mm | 9/16″0.5625 in · 14.29 mm | 0.065″1.65 mm |
| 1/4" USS | 5/16″0.3125 in · 7.94 mm | 0.734″0.734 in · 18.64 mm | 0.065″1.65 mm |
| 1/4" SAE | 9/32″0.28125 in · 7.14 mm | 5/8″0.625 in · 15.88 mm | 0.065″1.65 mm |
| 5/16" USS | 3/8″0.375 in · 9.52 mm | 7/8″0.875 in · 22.22 mm | 0.083″2.11 mm |
| 5/16" SAE | 11/32″0.34375 in · 8.73 mm | 11/16″0.6875 in · 17.46 mm | 0.065″1.65 mm |
| 3/8" USS | 7/16″0.4375 in · 11.11 mm | 1″1 in · 25.40 mm | 0.083″2.11 mm |
| 3/8" SAE | 13/32″0.40625 in · 10.32 mm | 13/16″0.8125 in · 20.64 mm | 0.065″1.65 mm |
| 7/16" USS | 1/2″0.5 in · 12.70 mm | 1 1/4″1.25 in · 31.75 mm | 0.083″2.11 mm |
| 7/16" SAE | 15/32″0.46875 in · 11.91 mm | 15/16″0.9375 in · 23.81 mm | 0.065″1.65 mm |
| 1/2" USS | 9/16″0.5625 in · 14.29 mm | 1 3/8″1.375 in · 34.92 mm | 0.109″2.77 mm |
| 1/2" SAE | 17/32″0.53125 in · 13.49 mm | 1 1/16″1.0625 in · 26.99 mm | 0.095″2.41 mm |
| 9/16" USS | 5/8″0.625 in · 15.88 mm | 1 15/32″1.46875 in · 37.31 mm | 0.109″2.77 mm |
| 9/16" SAE | 19/32″0.59375 in · 15.08 mm | 1 5/32″1.15625 in · 29.37 mm | 0.095″2.41 mm |
| 5/8" USS | 11/16″0.6875 in · 17.46 mm | 1 3/4″1.75 in · 44.45 mm | 0.134″3.40 mm |
| 5/8" SAE | 21/32″0.65625 in · 16.67 mm | 1 5/16″1.3125 in · 33.34 mm | 0.095″2.41 mm |
| 3/4" USS | 13/16″0.8125 in · 20.64 mm | 2″2 in · 50.80 mm | 0.148″3.76 mm |
| 3/4" SAE | 13/16″0.8125 in · 20.64 mm | 1 15/32″1.46875 in · 37.31 mm | 0.134″3.40 mm |
| 7/8" USS | 15/16″0.9375 in · 23.81 mm | 2 1/4″2.25 in · 57.15 mm | 0.165″4.19 mm |
| 7/8" SAE | 15/16″0.9375 in · 23.81 mm | 1 3/4″1.75 in · 44.45 mm | 0.134″3.40 mm |
| 1" USS | 1 1/16″1.0625 in · 26.99 mm | 2 1/2″2.5 in · 63.50 mm | 0.165″4.19 mm |
| 1" SAE | 1 1/16″1.0625 in · 26.99 mm | 2″2 in · 50.80 mm | 0.134″3.40 mm |
| 1 1/8" USS | 1 1/4″1.25 in · 31.75 mm | 2 3/4″2.75 in · 69.85 mm | 0.165″4.19 mm |
| 1 1/4" USS | 1 3/8″1.375 in · 34.92 mm | 3″3 in · 76.20 mm | 0.165″4.19 mm |
| 1 3/8" USS | 1 1/2″1.5 in · 38.10 mm | 3 1/4″3.25 in · 82.55 mm | 0.18″4.57 mm |
| 1 1/2" USS | 1 5/8″1.625 in · 41.27 mm | 3 1/2″3.5 in · 88.90 mm | 0.18″4.57 mm |
| 1 5/8" USS | 1 3/4″1.75 in · 44.45 mm | 3 3/4″3.75 in · 95.25 mm | 0.18″4.57 mm |
| 1 3/4" USS | 1 7/8″1.875 in · 47.62 mm | 4″4 in · 101.60 mm | 0.18″4.57 mm |
| 2" USS | 2 1/8″2.125 in · 53.97 mm | 4 1/2″4.5 in · 114.30 mm | 0.213″5.41 mm |
Data basis: commercial USS/SAE dimensions from Bolt Depot. Thicknesses are reference values, not a complete tolerance or material specification. See source notes.
Metric Washer Size Chart
ISO 7089 normal-series flat washer reference in millimeters, covering the standard thread-size series shown here from M1.6 through M64. Minimum and maximum ID, OD and thickness values are listed so the chart does not confuse nominal dimensions with tolerance limits. ISO lists ISO 7089:2000 as the current published edition while a replacement edition is under development. Sources [3]–[4]
| Fastener size | Inside diameter d1 (mm) | Outside diameter d2 (mm) | Thickness h (mm) |
|---|---|---|---|
| M1.6 | 1.7–1.84 | 3.7–4 | 0.25–0.35 |
| M2 | 2.2–2.34 | 4.7–5 | 0.25–0.35 |
| M2.5 | 2.7–2.84 | 5.7–6 | 0.45–0.55 |
| M3 | 3.2–3.38 | 6.64–7 | 0.45–0.55 |
| M3.5 | 3.7–3.88 | 7.64–8 | 0.45–0.55 |
| M4 | 4.3–4.48 | 8.64–9 | 0.7–0.9 |
| M5 | 5.3–5.48 | 9.64–10 | 0.9–1.1 |
| M6 | 6.4–6.62 | 11.57–12 | 1.4–1.8 |
| M8 | 8.4–8.62 | 15.57–16 | 1.4–1.8 |
| M10 | 10.5–10.77 | 19.48–20 | 1.8–2.2 |
| M12 | 13–13.27 | 23.48–24 | 2.3–2.7 |
| M14 | 15–15.27 | 27.48–28 | 2.3–2.7 |
| M16 | 17–17.27 | 29.48–30 | 2.7–3.3 |
| M18 | 19–19.33 | 33.38–34 | 2.7–3.3 |
| M20 | 21–21.33 | 36.38–37 | 2.7–3.3 |
| M22 | 23–23.33 | 38.38–39 | 2.7–3.3 |
| M24 | 25–25.33 | 43.38–44 | 3.7–4.3 |
| M27 | 28–28.33 | 49.38–50 | 3.7–4.3 |
| M30 | 31–31.39 | 55.26–56 | 3.7–4.3 |
| M33 | 34–34.62 | 58.8–60 | 4.4–5.6 |
| M36 | 37–37.62 | 64.8–66 | 4.4–5.6 |
| M39 | 42–42.62 | 70.8–72 | 5.4–6.6 |
| M42 | 45–45.62 | 76.8–78 | 7–9 |
| M45 | 48–48.62 | 83.6–85 | 7–9 |
| M48 | 52–52.74 | 90.6–92 | 7–9 |
| M52 | 56–56.74 | 96.6–98 | 7–9 |
| M56 | 62–62.74 | 103.6–105 | 9–11 |
| M60 | 66–66.74 | 108.6–110 | 9–11 |
| M64 | 70–70.74 | 113.6–115 | 9–11 |
Important: ISO 7089 also specifies requirements beyond these dimensions, including product grade and hardness classes. Use the controlled standard and purchase specification for design, procurement or acceptance inspection.
Washer Dimensions: ID, OD and Thickness
SAE vs USS Washers
SAE and USS are commercial dimensional patterns in the inch reference above. At many shared nominal sizes, USS washers have a larger outside diameter and sometimes a larger hole or thickness. Compare the actual row values before substituting one family for the other.
1/2" SAE
- ID
- 17/32" (0.53125 in)
- OD
- 1-1/16" (1.0625 in)
- Thickness
- 0.095 in
1/2" USS
- ID
- 9/16" (0.5625 in)
- OD
- 1-3/8" (1.375 in)
- Thickness
- 0.109 in
For example, a 1.10-inch seating pocket can accommodate the listed 1/2-inch SAE OD but not the listed 1/2-inch USS OD. That only establishes dimensional fit; material, hardness, contact pressure and joint requirements still control suitability.
How to Measure a Washer
Measure all three dimensions when identifying an unknown washer. OD alone can match more than one washer family.
Measure inside diameter
Use the inside jaws of a caliper across the center hole. Compare the physical hole to the chart’s ID or d1 value.
Measure outside diameter
Use the outside jaws across the widest part of the washer. Keep the caliper square to the washer faces.
Measure thickness
Measure across clean, flat faces away from burrs, deformation or coatings that could distort the reading.
Identify a Washer by Measurements
Enter caliper measurements to find the closest entry in the reference data on this page. This is an identification aid, not a compliance or tolerance check.
The matcher compares the entered dimensions with the inch-series reference and metric normal-series ranges on this page. If the closest result is still materially different, the washer may belong to another series, be worn/deformed, or require a controlled tolerance check.
How to Choose a Flat Washer
Start with the fastener size and required clearance, then confirm the available bearing area and stack height. The inside diameter must clear the fastener shank and any feature it passes over. The outside diameter must fit the seating surface without riding on a shoulder, radius or unsupported edge. Thickness changes the grip stack and remaining thread engagement.
A larger outside diameter can spread contact over more area, but it is not automatically better. For structural, high-strength, sealing or locking applications, use the washer type, material, hardness and standard required by the drawing or governing specification.
Washer Types and Limits of This Chart
Flat washer
Covered. Basic ID, OD and thickness geometry for the referenced flat-washer series.
Fender / large OD washer
Different series. Uses a larger outside diameter for broader coverage and should not be inferred from the USS chart.
Structural washer
Specification controlled. Hardened structural washers can have different dimensional and material requirements.
Lock or spring washer
Different function. A plain flat washer does not automatically replace locking or spring hardware.
Standards and Data Basis
Inch context: ASME B18.21.1 covers dimensional requirements, physical properties and related test methods for inch-series plain washers among other washer types. The SAE/USS table on this page is a commercial dimensional reference sourced from Bolt Depot; it is not represented as a verbatim reproduction of the ASME standard. Source [2]
Metric context: ISO 7089:2000 is the current published ISO standard for normal-series, product-grade-A plain washers; ISO also lists a replacement edition under development. The metric chart above follows the ISO 7089 thread-size series and dimensional ranges published by the cited secondary dimensional reference. It is a convenient reference, not a reproduction of the controlled ISO document. Sources [3]–[4]
Reference basis checked September 30, 2026. Standards and supplier data can change; the applicable drawing, purchase specification and controlled edition govern.
Sources
- Bolt Depot — USS and SAE Washer Dimensions. Commercial reference dimensions for the two inch-series families used in the primary chart.
- ASME B18.21.1 — Washers: Helical Spring-Lock, Tooth Lock, and Plain Washers (Inch Series). Standards context for inch-series plain washers.
- ISO 7089:2000 — Plain washers — Normal series — Product grade A. Current published ISO normal-series standard status.
- Global Fastener — ISO 7089:2000 dimensional reference. Public dimensional reference used to cross-check the ISO 7089 thread-size series and min/max ID, OD and thickness values shown in the metric chart.
Washer Size Chart FAQ
Is washer size the inside diameter?
No. The nominal washer size normally identifies the fastener it is intended to fit. The physical hole is larger to provide clearance, so use the ID or d1 column when you need the actual hole dimension.
What size washer fits a 1/4-inch bolt?
A nominal 1/4-inch flat washer is the starting point, but SAE and USS patterns differ. In this chart, 1/4-inch SAE is listed at 9/32-inch ID and 5/8-inch OD, while 1/4-inch USS is listed at 5/16-inch ID and 0.734-inch OD.
What size washer fits a 3/8-inch bolt?
Use a nominal 3/8-inch washer in the required family. The chart lists 3/8-inch SAE at 13/32-inch ID and 13/16-inch OD, and 3/8-inch USS at 7/16-inch ID and 1-inch OD.
What size washer fits a 1/2-inch bolt?
A nominal 1/2-inch washer is the normal starting size. The chart lists 1/2-inch SAE at 17/32-inch ID and 1-1/16-inch OD, while 1/2-inch USS is 9/16-inch ID and 1-3/8-inch OD.
What size washer fits an M8 bolt?
For the metric normal-series reference above, the M8 entry has an inside-diameter range of 8.4–8.62 mm, an outside-diameter range of 15.57–16 mm and a thickness range of 1.4–1.8 mm. Verify the specified metric washer standard before procurement.
What is the difference between SAE and USS washers?
They are different commercial dimensional patterns. At many shared nominal fastener sizes, USS washers have a larger outside diameter and may also differ in inside diameter and thickness. Compare the actual chart values rather than choosing by acronym alone.
What do ID and OD mean on a washer?
ID means inside diameter—the diameter of the center hole. OD means outside diameter—the full diameter across the outer edge of the washer.
Why is a washer hole larger than the bolt?
The hole needs installation clearance around the fastener shank. That is why a nominal 1/2-inch or M8 washer does not have a hole measuring exactly 1/2 inch or 8.00 mm.
How do I measure an unknown washer?
Measure the inside diameter, outside diameter and thickness with calipers, then compare all three values with the appropriate washer family or standard. Do not identify the washer from OD alone.
Does this chart give manufacturing tolerances?
The inch table lists the cited supplier reference dimensions. The metric table includes published min/max dimensional ranges from the cited secondary reference. For acceptance inspection, use the applicable controlled standard or purchase specification.