M3 - Basic Thread Dimensions

Property mm Inch
Nominal Diameter 3 0.1181
Pitch (Distance) 0.5 0.0197
Pitch Diameter 2.675 0.1053
Minor Diameter 2.459 0.0968
Thread Height 0.271 0.0107
Addendum 0.162 0.0064
Crest (External)
Root (Internal)		 0.063 0.0025
Tap Drill Size
(75% depth)		 2.51 0.099
Lead Angle
(Single Start)		 3.4°
Thread Family Metric Coarse Pitch (MC)
Relevant Standards ISO 68-1, ISO 9651-1, ISO 965-2, ISO 261,DIN 13
Equivalent Inch Thread#4 - 48 UNF

For more threading data scroll down, or use the Thread Calculator

Table of Content

M3 Possible Thread Classes

External Threads

Choose tolerance class: 4g, 4h, 6e, 6g, 6h, 5g4g, 5h4h, 5g6g, 7g6g, 7h6h, 7e6e

Metric ISO External Thread - Tolerance sketch

Internal Threads

Choose tolerance class: 4H, 5H, 5G, 6H, 6G, 7H, 7G

Metric ISO Internal Thread - Tolerance sketch

M3 4g (External)

* Permisable values for thread Class 4g

# Description Value (mm) Value (Inch)
es Allowance 0.02 (Ref) 0.0008 (Ref)
d Major Diameter 2.913 - 2.98 0.1147 - 0.1173
d2 Pitch Diameter 2.607 - 2.655 0.1026 - 0.1045
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.127 0.0025 - 0.005
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 4h (External)

* Permisable values for thread Class 4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 2.933 - 3 0.1155 - 0.1181
d2 Pitch Diameter 2.627 - 2.675 0.1034 - 0.1053
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.127 0.0025 - 0.005
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 6e (External)

* Permisable values for thread Class 6e

# Description Value (mm) Value (Inch)
es Allowance 0.05 (Ref) 0.002 (Ref)
d Major Diameter 2.844 - 2.95 0.112 - 0.1161
d2 Pitch Diameter 2.55 - 2.625 0.1004 - 0.1033
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.144 0.0025 - 0.0057
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 6g (External)

* Permisable values for thread Class 6g

# Description Value (mm) Value (Inch)
es Allowance 0.02 (Ref) 0.0008 (Ref)
d Major Diameter 2.874 - 2.98 0.1131 - 0.1173
d2 Pitch Diameter 2.58 - 2.655 0.1016 - 0.1045
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.144 0.0025 - 0.0057
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 6h (External)

* Permisable values for thread Class 6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 2.894 - 3 0.1139 - 0.1181
d2 Pitch Diameter 2.6 - 2.675 0.1024 - 0.1053
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.144 0.0025 - 0.0057
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 5g4g (External)

* Permisable values for thread Class 5g4g

# Description Value (mm) Value (Inch)
es Allowance 0.02 (Ref) 0.0008 (Ref)
d Major Diameter 2.913 - 2.98 0.1147 - 0.1173
d2 Pitch Diameter 2.595 - 2.655 0.1022 - 0.1045
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.135 0.0025 - 0.0053
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 5h4h (External)

* Permisable values for thread Class 5h4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 2.933 - 3 0.1155 - 0.1181
d2 Pitch Diameter 2.615 - 2.675 0.103 - 0.1053
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.135 0.0025 - 0.0053
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 5g6g (External)

* Permisable values for thread Class 5g6g

# Description Value (mm) Value (Inch)
es Allowance 0.02 (Ref) 0.0008 (Ref)
d Major Diameter 2.874 - 2.98 0.1131 - 0.1173
d2 Pitch Diameter 2.595 - 2.655 0.1022 - 0.1045
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.135 0.0025 - 0.0053
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

* Back to Thread Class Selection

M3 7g6g (External)

* Permisable values for thread Class 7g6g

# Description Value (mm) Value (Inch)
es Allowance 0.02 (Ref) 0.0008 (Ref)
d Major Diameter 2.874 - 2.98 0.1131 - 0.1173
d2 Pitch Diameter 2.56 - 2.655 0.1008 - 0.1045
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.155 0.0025 - 0.0061
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 7h6h (External)

* Permisable values for thread Class 7h6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 2.894 - 3 0.1139 - 0.1181
d2 Pitch Diameter 2.58 - 2.675 0.1016 - 0.1053
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.155 0.0025 - 0.0061
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 7e6e (External)

* Permisable values for thread Class 7e6e

# Description Value (mm) Value (Inch)
es Allowance 0.05 (Ref) 0.002 (Ref)
d Major Diameter 2.844 - 2.95 0.112 - 0.1161
d2 Pitch Diameter 2.53 - 2.625 0.0996 - 0.1033
R Root Radius 0.063 (Min) 0.0025 (Min)
C Root Truncation 0.063 - 0.155 0.0025 - 0.0061
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 4H (Internal)

* Permisable values for thread Class 4H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 2.459 - 2.549 0.0968 - 0.1004
D2 Pitch Diameter 2.675 - 2.738 0.1053 - 0.1078
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 5H (Internal)

* Permisable values for thread Class 5H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 2.459 - 2.571 0.0968 - 0.1012
D2 Pitch Diameter 2.675 - 2.755 0.1053 - 0.1085
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 5G (Internal)

* Permisable values for thread Class 5G

# Description Value (mm) Value (Inch)
EL Allowance 0.02 (Ref) 0.0008 (Ref)
D1 Minor Diameter 2.479 - 2.591 0.0976 - 0.102
D2 Pitch Diameter 2.695 - 2.775 0.1061 - 0.1093
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 6H (Internal)

* Permisable values for thread Class 6H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 2.459 - 2.599 0.0968 - 0.1023
D2 Pitch Diameter 2.675 - 2.775 0.1053 - 0.1093
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

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M3 6G (Internal)

* Permisable values for thread Class 6G

# Description Value (mm) Value (Inch)
EL Allowance 0.02 (Ref) 0.0008 (Ref)
D1 Minor Diameter 2.479 - 2.619 0.0976 - 0.1031
D2 Pitch Diameter 2.695 - 2.795 0.1061 - 0.11
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

* Back to Thread Class Selection

M3 7H (Internal)

* Permisable values for thread Class 7H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 2.459 - 2.639 0.0968 - 0.1039
D2 Pitch Diameter 2.675 - 2.8 0.1053 - 0.1102
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

* Back to Thread Class Selection

M3 7G (Internal)

* Permisable values for thread Class 7G

# Description Value (mm) Value (Inch)
EL Allowance 0.02 (Ref) 0.0008 (Ref)
D1 Minor Diameter 2.479 - 2.659 0.0976 - 0.1047
D2 Pitch Diameter 2.695 - 2.82 0.1061 - 0.111
D Major Diameter 3 (Min) 0.1181 (Min)
LE Normal Length of Engagement 1.5 - 4.5 0.0591 - 0.1772

* Back to Thread Class Selection

Tap Drill Sizes for M3

  • If not specified, assume a thread depth of 75%.
  • You can learn more about thread depth in tapping here.
  • To get the tap drill size in other depths, use our Tap Drill Size Calculator .
Thread Depth Tap Drill Size (Inch) Tap Drill Size (mm)
55% 0.104 2.64
60% 0.103 2.61
65% 0.101 2.58
70% 0.100 2.55
75% 0.099 2.51
80% 0.098 2.48
85% 0.096 2.45

Over Wire Measurements for M3


* OverWire is a measuring method to obatin the pitch diameter of threads. It is mostly used when a manufacturer does not have a Go/Nogo gauge for a thread. You can learn more about it here

mm Inch
Permissible Wire Diameter Range 0.253 - 0.505 0.0099 - 0.0199
Ideal Wire Diameter 0.289 0.0114
Possible Wires
From Standard Sets		 * 0.26
* 0.289
* 0.346
* 0.404
* 0.433
* 0.462
 * 0.0103
* 0.0116
* 0.012
* 0.0131
* 0.0144
* 0.016
* 0.018
* 0.0193

Once you knoe your wire diameter, you need to find out what is the premissable Measurement for your pitch diameter (Depending on the class). Use our Over Wire Calculator to find out!


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