Metric Washer Dimensions

WHAT IS THE REAL PURPOSE OF WASHERS AND WHY ARE THEY USED?

LOAD DISTRIBUTION

The primary purpose of washers is to reduce the risk of damage and distribute the load of the threaded fastener with which they are used[cite: 4].

Threaded fasteners stress the material that they are driven into. For example, driving a screw into a wooden surface may crack the surface and damage the internal grain structure[cite: 4].

Not all materials require washers, but for wood and other softer materials, it is generally safer to incorporate washers to spread the load over a larger area[cite: 4].

SPACING

Washers can also be used as spacers[cite: 4]. Dimensions shown are in mm, if you wish to convert to inches, please use our universal converter[cite: 4].

We also have information on Imperial Washers.

METRIC - FLAT WASHER DIMENSIONS - BS4320 FORM A

[cite: 4]

[cite: 4]

Nominal Size	Inside Dia (d1)	Outside Dia (d2)	Thickness (h)
M3	3.2	7.0	0.5
M4	4.3	9.0	0.8
M5	5.3	10.0	1.0
M6	6.4	12.0	1.6
M8	8.4	16.0	1.6
M10	10.5	20.0	2.0
M12	13.0	24.0	2.5

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METRIC - SPRING WASHER DIMENSIONS - BS4464

[cite: 4]

[cite: 4]

Nominal Size	Inside Dia (d1)	Outside Dia (d2)	Thickness (h)
M3	3.1	6.2	0.8
M4	4.1	7.6	0.9
M5	5.1	9.2	1.2
M6	6.1	11.8	1.6
M8	8.1	14.8	2.0
M10	10.2	18.1	2.2
M12	12.2	21.1	2.5

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METRIC - INTERNAL TOOTH WASHER DIMENSIONS - BS4320

[cite: 4]

[cite: 4]

Nominal Size	Inside Dia (d1)	Outside Dia (d2)
M3	3.2	6.0
M4	4.3	8.0
M5	5.3	10.0
M6	6.4	11.0
M8	8.4	15.0
M10	10.5	18.0
M12	13.0	20.5

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METRIC - EXTERNAL TOOTH WASHER DIMENSIONS - BS4320

[cite: 4]

[cite: 4]

Nominal Size	Inside Dia (d1)	Outside Dia (d2)
M3	3.2	6.0
M4	4.3	8.0
M5	5.3	10.0
M6	6.4	11.0
M8	8.4	15.0
M10	10.5	18.0
M12	13.0	20.5