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ISO Metric Thread Tolerance Tables

The information below can be used to calculate the values of thread tolerances defined by ISO 965/1.

Tolerances are written as a combination of a tolerance band, signified by an alphabetic letter, and a tolerance class, signified by a number. For the tolerance band, uppercase letters (E or G) signify internal threads whilst lowercase letters (e, f, g or h) signify external threads. Grade 6 is an example of a tolerance class which signifies general use, with smaller numbers being used for stricter tolerance and higher numbers being used for more loose tolerances.

For instance, a 5g tolerance for an external thread would signify a tolerance that is in the 5th class of band g (see diagram below for reference).

Screw threads are usually signified by two tolerances. One is for the maximum outside diameter, measured from the major diameter of the thread, and the other is for the pitch diameter, measured from the midpoint of each tooth.

For more information on measuring thread diameters and pitch diameters, please see our article on How To Measure Screws.

As an example, a common screw thread tolerance is 5g6g, which indicates a 5g tolerance on its pitch diameter, and a 6g tolerance on its external (thread) diameter.

Screw threads with identical external tolerances and pitch tolerances are expressed with a single tolerance letter and number. For instance, for a screw with both a 6g major diameter tolerance and a 6g pitch diameter tolerance, this would simply be written as “6g”.

The reason that the values for tolerance bands (signified by letters, found in table 1) are written as positive and negative numbers, and the values for tolerance classes (written as numbers, found in tables 2 - 5) are not, is because tolerance classes are applied interchangeably to both internal and external threads, and must be either subtracted or added to a tolerance, dependent on whether the thread is internal or external.

Important Formulae
D Major Diameter
D1 Minor Diameter Internal Thread
D2 Pitch Diameter Internal Thread
d Major Diameter External Thread
d1 Minor Diameter External Thread
d2 Pitch Diameter External Thread
T Tolerance
TD1 Tolerance for D1
TD2 Tolerance for D2
Td1 Tolerance for d1
Td2 Tolerance for d2
EI Lower Deviation Internal Thread
ES Upper Deviation Internal Thread
ei Lower Deviation External Thread
es Upper Deviation External Thread

 

Important Calculations
Internal Threads
Min major dia. basic major dia. + EI (Table 1)
Max minor dia. min minor dia. + TD1 (Table 2)
Max pitch dia. min pitch dia. + TD2 (Table 4)
External Threads
Max major dia. basic major dia. − es (Table 1)
Min major dia. max major dia. − Td (Table 3)
Min pitch dia. max pitch dia. − Td2 (Table 5)

 

Diagram representing the minor and major diameter tolerances of internal and external threads. This diagram is colour-coded with the tables below.

Table 1: Fundamental Deviation Codes For Internal and External Metric Threads (EI/es)
Pitch Allowance (Fundamental Deviation)
External Thread Internal Thread
e f g h H G
es es es es EI EI
0.2 N/A N/A -0.017 0 0 +0.017
0.25 N/A N/A -0.018 0 0 +0.018
0.3 N/A N/A -0.018 0 0 +0.018
0.35 N/A -0.034 -0.019 0 0 +0.019
0.4 N/A -0.034 -0.019 0 0 +0.019
0.45 N/A -0.035 -0.020 0 0 +0.020
0.5 -0.050 -0.036 -0.020 0 0 +0.020
0.6 -0.053 -0.036 -0.021 0 0 +0.021
0.7 -0.056 -0.038 -0.022 0 0 +0.022
0.75 -0.056 -0.038 -0.022 0 0 +0.022
0.8 -0.060 -0.038 -0.024 0 0 +0.024
1 -0.060 -0.040 -0.026 0 0 +0.026
1.25 -0.063 -0.042 -0.028 0 0 +0.028
1.5 -0.067 -0.045 -0.032 0 0 +0.032
1.75 -0.071 -0.048 -0.034 0 0 +0.034
2 -0.071 -0.052 -0.038 0 0 +0.038
2.5 -0.080 -0.058 -0.042 0 0 +0.042
3 -0.085 -0.063 -0.048 0 0 +0.048
3.5 -0.090 -0.070 -0.053 0 0 +0.053
4 -0.095 -0.075 -0.060 0 0 +0.060
4.5 -0.100 -0.080 -0.063 0 0 +0.063
5 -0.106 -0.085 -0.071 0 0 +0.071
5.5 -0.112 -0.090 -0.075 0 0 +0.075
6 -0.118 -0.095 -0.080 0 0 +0.080

 

Table 2: Minor Diameter Tolerance of Internal Metric Threads (TD1)
Pitch 4 5 6 7 8
0.2 0.038 N/A N/A N/A N/A
0.25 0.045 0.056 N/A N/A N/A
0.3 0.053 0.067 0.085 N/A N/A
0.35 0.063 0.080 0.100 N/A N/A
0.4 0.071 0.090 0.112 N/A N/A
0.45 0.080 0.100 0.125 N/A N/A
0.5 0.090 0.112 0.140 0.180 N/A
0.6 0.100 0.125 0.160 0.200 N/A
0.7 0.112 0.140 0.180 0.224 N/A
0.75 0.118 0.150 0.190 0.236 N/A
0.8 0.125 0.160 0.200 0.250 0.315
1 0.150 0.190 0.236 0.300 0.375
1.25 0.170 0.212 0.265 0.335 0.425
1.5 0.190 0.236 0.300 0.375 0.475
1.75 0.212 0.265 0.335 0.425 0.530
2 0.236 0.300 0.375 0.475 0.600
2.5 0.280 0.355 0.450 0.560 0.710
3 0.315 0.400 0.500 0.630 0.800
3.5 0.355 0.450 0.560 0.710 0.900
4 0.375 0.475 0.600 0.750 0.950
4.5 0.425 0.530 0.670 0.850 1.060
5 0.450 0.560 0.710 0.900 1.120
5.5 0.475 0.600 0.750 0.950 1.180
6 0.500 0.630 0.800 1.000 1.250

 

Table 3: Major Diameter Tolerance of External Metric Threads (Td)
Pitch Tolerance Grade
4 6 8
0.2 0.036 0.056 N/A
0.25 0.042 0.067 N/A
0.3 0.048 0.075 N/A
0.35 0.053 0.085 N/A
0.4 0.060 0.095 N/A
0.45 0.063 0.100 N/A
0.5 0.067 0.106 N/A
0.6 0.080 0.125 N/A
0.7 0.090 0.140 N/A
0.75 0.090 0.140 N/A
0.8 0.095 0.150 0.236
1 0.112 0.180 0.280
1.25 0.132 0.212 0.335
1.5 0.150 0.236 0.375
1.75 0.170 0.265 0.425
2 0.180 0.280 0.450
2.5 0.212 0.335 0.530
3 0.236 0.375 0.600
3.5 0.265 0.425 0.670
4 0.300 0.475 0.750
4.5 0.315 0.500 0.800
5 0.335 0.530 0.850
5.5 0.355 0.560 0.900
6 0.375 0.600 0.950

 

Table 4: Pitch Diameter Tolerance for Internal Metric Threads (TD2)
Basic Major Diameter Pitch  Tolerance Grade
Over Up to and Including 4 5 6 7 8
1.5     2.8     0.2 0.042 N/A N/A N/A N/A
0.25 0.048 0.060 N/A N/A N/A
0.35 0.053 0.067 0.085 N/A N/A
0.4 0.056 0.071 0.090 N/A N/A
0.45 0.060 0.075 0.095 N/A N/A
2.8      5.6      0.35 0.056 0.071 0.090 N/A N/A
0.5 0.063 0.080 0.100 0.125 N/A
0.6 0.071 0.090 0.112 0.140 N/A
0.7 0.075 0.095 0.118 0.150 N/A
0.75 0.075 0.095 0.118 0.150 N/A
0.8 0.080 0.100 0.125 0.160 0.200
5.6    11.2    0.75 0.085 0.106 0.132 0.170 N/A
1 0.095 0.118 0.150 0.190 0.236
1.25 0.100 0.125 0.160 0.200 0.250
1.5 0.112 0.140 0.180 0.224 0.280
11.2      22.4      1 0.100 0.125 0.160 0.200 0.250
1.25 0.112 0.140 0.180 0.224 0.280
1.5 0.118 0.150 0.190 0.236 0.300
1.75 0.125 0.160 0.200 0.250 0.315
2 0.132 0.170 0.212 0.265 0.335
2.5 0.140 0.180 0.224 0.280 0.355
22.4       45       1 0.106 0.132 0.170 0.212 N/A
1.5 0.125 0.160 0.200 0.250 0.315
2 0.140 0.180 0.224 0.280 0.355
3 0.170 0.212 0.265 0.335 0.425
3.5 0.180 0.224 0.280 0.355 0.450
4 0.190 0.236 0.300 0.375 0.475
4.5 0.200 0.250 0.315 0.400 0.500
45       90       1.5 0.132 0.170 0.212 0.265 0.335
2 0.150 0.190 0.236 0.300 0.375
3 0.180 0.224 0.280 0.355 0.450
4 0.200 0.250 0.315 0.400 0.500
5 0.212 0.265 0.335 0.425 0.530
5.5 0.224 0.280 0.355 0.450 0.560
6 0.236 0.300 0.375 0.475 0.600
90    180    2 0.160 0.200 0.250 0.315 0.400
3 0.190 0.236 0.300 0.375 0.475
4 0.212 0.265 0.335 0.425 0.530
6 0.250 0.315 0.400 0.500 0.630
180   355   3 0.212 0.265 0.335 0.425 0.530
4 0.236 0.300 0.375 0.475 0.600
6 0.265 0.335 0.425 0.530 0.670

 

Table 5: Pitch Diameter Tolerance for External Metric Threads (Td2)
Basic Major Diameter Pitch  Tolerance Grade
Over Up to and Including 3 4 5 6 7 8 9
1.5     2.8     0.2 0.025 0.032 0.040 0.050 N/A N/A N/A
0.25 0.028 0.036 0.045 0.056 N/A N/A N/A
0.35 0.032 0.040 0.050 0.063 0.080 N/A N/A
0.4 0.034 0.042 0.053 0.067 0.085 N/A N/A
0.45 0.036 0.045 0.056 0.071 0.090 N/A N/A
2.8      5.6      0.35 0.034 0.042 0.053 0.067 0.085 N/A N/A
0.5 0.038 0.048 0.060 0.075 0.095 N/A N/A
0.6 0.042 0.053 0.067 0.085 0.106 N/A N/A
0.7 0.045 0.056 0.071 0.090 0.112 N/A N/A
0.75 0.045 0.056 0.071 0.090 0.112 N/A N/A
0.8 0.048 0.060 0.075 0.095 0.118 0.150 0.190
5.6    11.2    0.75 0.050 0.063 0.080 0.100 0.125 N/A N/A
1 0.056 0.071 0.090 0.112 0.140 0.180 0.224
1.25 0.060 0.075 0.095 0.118 0.150 0.190 0.236
1.5 0.067 0.085 0.106 0.132 0.170 0.212 0.265
11.2      22.4      1 0.060 0.075 0.095 0.118 0.150 0.190 0.236
1.25 0.067 0.085 0.106 0.132 0.170 0.212 0.265
1.5 0.071 0.090 0.112 0.140 0.180 0.224 0.280
1.75 0.075 0.095 0.118 0.150 0.190 0.236 0.300
2 0.080 0.100 0.125 0.160 0.200 0.250 0.315
2.5 0.085 0.106 0.132 0.170 0.212 0.265 0.335
22.4       45       1 0.063 0.080 0.100 0.125 0.160 0.200 0.250
1.5 0.075 0.095 0.118 0.150 0.190 0.236 0.300
2 0.085 0.106 0.132 0.170 0.212 0.265 0.335
3 0.100 0.125 0.160 0.200 0.250 0.315 0.400
3.5 0.106 0.132 0.170 0.212 0.265 0.335 0.425
4 0.112 0.140 0.180 0.224 0.280 0.355 0.450
4.5 0.118 0.150 0.190 0.236 0.300 0.375 0.475
45       90       1.5 0.080 0.100 0.125 0.160 0.200 0.250 0.315
2 0.090 0.112 0.140 0.180 0.224 0.280 0.355
3 0.106 0.132 0.170 0.212 0.265 0.335 0.425
4 0.118 0.150 0.190 0.236 0.300 0.375 0.475
5 0.125 0.160 0.200 0.250 0.315 0.400 0.500
5.5 0.132 0.170 0.212 0.265 0.335 0.425 0.530
6 0.140 0.180 0.224 0.280 0.355 0.450 0.560
90    180    2 0.095 0.118 0.150 0.190 0.236 0.300 0.375
3 0.112 0.140 0.180 0.224 0.280 0.355 0.450
4 0.125 0.160 0.200 0.250 0.315 0.400 0.500
6 0.150 0.190 0.236 0.300 0.375 0.475 0.600
180   355   3 0.125 0.160 0.200 0.250 0.315 0.400 0.500
4 0.140 0.180 0.224 0.280 0.355 0.450 0.560
6 0.160 0.200 0.250 0.315 0.400 0.500 0.630
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