Flat Washer Size Chart
Compare common flat washer dimensions by nominal bolt size. USS washers generally have larger inside and outside diameters than SAE washers, although hole sizes may coincide at some larger sizes. Dimensions are reference values, not guaranteed measurements for every manufacturer.
SAE vs USS F436 HardenedMetric DIN 125 Metric Large ODSAE & USS Flat Washers
Inches. Typical commercial washer dimensions and published thickness ranges. SAE and USS inside diameters are listed separately; actual hole sizes, outside diameters and thicknesses vary by supplier and specification. A dash indicates a USS size not commonly listed in standard commercial charts.
| Bolt size | SAE ID (in) | USS ID (in) | SAE OD (in) | USS OD (in) | SAE thickness (in), min–max | USS thickness (in), min–max |
|---|---|---|---|---|---|---|
| #6 | 0.156 | — | 0.375 | 0.438 | .036–.065 | — |
| #8 | 0.188 | — | 0.375 | 0.500 | .036–.065 | — |
| #10 | 0.219 | — | 0.438 | 0.562 | .036–.065 | — |
| 1/4" | 0.281 | 0.312 | 0.500 | 0.734 | .051–.080 | .051–.080 |
| 5/16" | 0.344 | 0.375 | 0.562 | 0.875 | .051–.080 | .064–.104 |
| 3/8" | 0.406 | 0.438 | 0.812 | 1.000 | .051–.080 | .064–.104 |
| 7/16" | 0.469 | 0.500 | 0.922 | 1.250 | .051–.080 | .064–.104 |
| 1/2" | 0.531 | 0.562 | 1.062 | 1.375 | .074–.121 | .086–.132 |
| 9/16" | 0.594 | 0.625 | 1.156 | 1.469 | .074–.121 | .086–.132 |
| 5/8" | 0.656 | 0.688 | 1.312 | 1.750 | .074–.121 | .108–.160 |
| 3/4" | 0.812 | 0.812 | 1.469 | 2.000 | .108–.160 | .122–.177 |
| 7/8" | 0.938 | 0.938 | 1.750 | 2.250 | .108–.160 | .136–.192 |
| 1" | 1.062 | 1.062 | 2.000 | 2.500 | .108–.160 | .136–.192 |
| 1-1/8" | 1.188 | 1.188 | 2.250 | 2.750 | .108–.160 | .136–.192 |
| 1-1/4" | 1.312 | 1.312 | 2.500 | 3.000 | .136–.192 | .136–.192 |
| 1-1/2" | 1.562 | 1.562 | 3.000 | 3.500 | .153–.213 | .153–.213 |
ASTM F436 Type 1 Hardened Washers
Circular standard-pattern hardened washers. ID, OD and thickness are specification ranges in inches. Not interchangeable with ordinary SAE/USS washers. Extra-thick F436 is a separate style (nominal 5/16 in thick).
| Bolt size | ID (in), min–max | OD (in), min–max | Thickness (in), min–max |
|---|---|---|---|
| 1/4" | .281–.313 | .593–.657 | .051–.080 |
| 5/16" | .344–.376 | .656–.720 | .051–.080 |
| 3/8" | .406–.438 | .781–.845 | .051–.080 |
| 7/16" | .469–.501 | .890–.954 | .051–.080 |
| 1/2" | .531–.563 | 1.031–1.095 | .097–.177 |
| 9/16" | .625–.657 | 1.156–1.220 | .110–.177 |
| 5/8" | .688–.720 | 1.281–1.345 | .122–.177 |
| 3/4" | .813–.845 | 1.436–1.500 | .122–.177 |
| 7/8" | .938–.970 | 1.718–1.782 | .136–.177 |
| 1" | 1.063–1.126 | 1.937–2.063 | .136–.177 |
| 1-1/8" | 1.188–1.251 | 2.187–2.313 | .136–.177 |
| 1-1/4" | 1.375–1.438 | 2.437–2.563 | .136–.177 |
| 1-3/8" | 1.500–1.563 | 2.687–2.813 | .136–.177 |
| 1-1/2" | 1.625–1.688 | 2.937–3.063 | .136–.177 |
Metric Flat Washers: DIN 125 / ISO 7089
Millimeters. Common normal-series metric washer dimensions; DIN 125 and ISO 7089 are broadly comparable, but verify specific product tolerances.
| Bolt size | ID (mm) | OD (mm) | Thickness (mm) |
|---|---|---|---|
| M3 | 3.2 | 7 | 0.5 |
| M4 | 4.3 | 9 | 0.8 |
| M5 | 5.3 | 10 | 1.0 |
| M6 | 6.4 | 12 | 1.6 |
| M8 | 8.4 | 16 | 1.6 |
| M10 | 10.5 | 20 | 2.0 |
| M12 | 13 | 24 | 2.5 |
| M14 | 15 | 28 | 2.5 |
| M16 | 17 | 30 | 3.0 |
| M18 | 19 | 34 | 3.0 |
| M20 | 21 | 37 | 3.0 |
| M22 | 23 | 39 | 3.0 |
| M24 | 25 | 44 | 4.0 |
| M27 | 28 | 50 | 4.0 |
| M30 | 31 | 56 | 4.0 |
Metric Large-OD Washers: DIN 9021 / ISO 7093
Millimeters. Large outside diameter (often called fender-style metric washers). Check supplier dimensions, particularly for larger sizes.
| Bolt size | ID (mm) | Large OD (mm) | Nominal thickness (mm) |
|---|---|---|---|
| M3 | 3.2 | 9 | 0.8 |
| M4 | 4.3 | 12 | 1.0 |
| M5 | 5.3 | 15 | 1.2 |
| M6 | 6.4 | 18 | 1.6 |
| M8 | 8.4 | 24 | 2.0 |
| M10 | 10.5 | 30 | 2.5 |
| M12 | 13 | 37 | 3.0 |
| M14 | 15 | 44 | 3.0 |
| M16 | 17 | 50 | 3.0 |
| M18 | 19 | 56 | 4.0 |
| M20 | 21 | 60 | 4.0 |
| M22 | 23 | 66 | 5.0 |
| M24 | 25 | 72 | 5.0 |
| M27 | 28 | 85 | 6.0 |
| M30 | 31 | 92 | 6.0 |
Important: Nominal washer size identifies the intended bolt, not the washer's actual inside diameter. SAE, USS, hardened structural, fender, and specialty washers are not interchangeable in every application. Check the actual product or manufacturer specification for fit, thickness, load rating, and tolerances.
Reference dimensions only. SAE/USS commercial washer thicknesses are typical published min–max ranges; ASTM F436 ranges apply to standard circular Type 1; metric thicknesses are nominal. Verify actual product and current specification for critical applications.