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 (E, G, e, f, g or h, with uppercase letters signifying internal threads, and lowercase signifying external), and a tolerance class, signified by a number. Grade 6 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 would signify a tolerance that is in the 5th tolerance class of band G.

Screw threads are usually signified by two tolerances, one for the maximum outside diameter measure from the major diameter of the thread, and one for the pitch diameter, measured from the midpoint of each tooth. For more information on measuring pitch diameter, see our article on how to measure a screw.

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

Screws threads with identical external tolerances and pitch tolerances are expressed with a single tolerance letter and number. For instance, a screw with a 6g major diameter tolerance and a 6g pitch diameter tolerance 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
DMajor Diameter
D1Minor Diameter Internal Thread
D2Pitch Diameter Internal Thread
dMajor Diameter External Thread
d1Minor Diameter External Thread
d2Pitch Diameter External Thread
TTolerance
TD1Tolerance for D1
TD2Tolerance for D2
Td1Tolerance for d1
Td2Tolerance for d2
EILower Deviation Internal Thread
ESUpper Deviation Internal Thread
eiLower Deviation External Thread
esUpper Deviation Internal 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)
PitchAllowance (Fundamental Deviation)
External ThreadInternal Thread
efghHG
esesesesEIEI
0.2N/AN/A-0.01700+0.017
0.25N/AN/A-0.01800+0.018
0.3N/AN/A-0.01800+0.018
0.35N/A-0.034-0.01900+0.019
0.4N/A-0.034-0.01900+0.019
0.45N/A-0.035-0.02000+0.020
0.5-0.050-0.036-0.02000+0.020
0.6-0.053-0.036-0.02100+0.021
0.7-0.056-0.038-0.02200+0.022
0.75-0.056-0.038-0.02200+0.022
0.8-0.060-0.038-0.02400+0.024
1-0.060-0.040-0.02600+0.026
1.25-0.063-0.042-0.02800+0.028
1.5-0.067-0.045-0.03200+0.032
1.75-0.071-0.048-0.03400+0.034
2-0.071-0.052-0.03800+0.038
2.5-0.080-0.058-0.04200+0.042
3-0.085-0.063-0.04800+0.048
3.5-0.090-0.070-0.05300+0.053
4-0.095-0.075-0.06000+0.060
4.5-0.100-0.080-0.06300+0.063
5-0.106-0.085-0.07100+0.071
5.5-0.112-0.090-0.07500+0.075
6-0.118-0.095-0.08000+0.080

Table 2: Minor Diameter Tolerance of Internal Metric Threads (TD1)
Pitch45678
0.20.038N/AN/AN/AN/A
0.250.0450.056N/AN/AN/A
0.30.0530.0670.085N/AN/A
0.350.0630.0800.100N/AN/A
0.40.0710.0900.112N/AN/A
0.450.0800.1000.125N/AN/A
0.50.0900.1120.1400.180N/A
0.60.1000.1250.1600.200N/A
0.70.1120.1400.1800.224N/A
0.750.1180.1500.1900.236N/A
0.80.1250.1600.2000.2500.315
10.1500.1900.2360.3000.375
1.250.1700.2120.2650.3350.425
1.50.1900.2360.3000.3750.475
1.750.2120.2650.3350.4250.530
20.2360.3000.3750.4750.600
2.50.2800.3550.4500.5600.710
30.3150.4000.5000.6300.800
3.50.3550.4500.5600.7100.900
40.3750.4750.6000.7500.950
4.50.4250.5300.6700.8501.060
50.4500.5600.7100.9001.120
5.50.4750.6000.7500.9501.180
60.5000.6300.8001.0001.250

Table 3: Major Diameter Tolerance of External Metric Threads (Td)
PitchTolerance Grade
468
0.20.0360.056N/A
0.250.0420.067N/A
0.30.0480.075N/A
0.350.0530.085N/A
0.40.0600.095N/A
0.450.0630.100N/A
0.50.0670.106N/A
0.60.0800.125N/A
0.70.0900.140N/A
0.750.0900.140N/A
0.80.0950.1500.236
10.1120.1800.280
1.250.1320.2120.335
1.50.1500.2360.375
1.750.1700.2650.425
20.1800.2800.450
2.50.2120.3350.530
30.2360.3750.600
3.50.2650.4250.670
40.3000.4750.750
4.50.3150.5000.800
50.3350.5300.850
5.50.3550.5600.900
60.3750.6000.950

Table 4: Pitch Diameter Tolerance for Internal Metric Threads (TD2)
Basic Major DiameterPitch Tolerance Grade
OverUp to and Including45678
1.5    2.8    0.20.042N/AN/AN/AN/A
0.250.0480.060N/AN/AN/A
0.350.0530.0670.085N/AN/A
0.40.0560.0710.090N/AN/A
0.450.0600.0750.095N/AN/A
2.8     5.6     0.350.0560.0710.090N/AN/A
0.50.0630.0800.1000.125N/A
0.60.0710.0900.1120.140N/A
0.70.0750.0950.1180.150N/A
0.750.0750.0950.1180.150N/A
0.80.0800.1000.1250.1600.200
5.6   11.2   0.750.0850.1060.1320.170N/A
10.0950.1180.1500.1900.236
1.250.1000.1250.1600.2000.250
1.50.1120.1400.1800.2240.280
11.2     22.4     10.1000.1250.1600.2000.250
1.250.1120.1400.1800.2240.280
1.50.1180.1500.1900.2360.300
1.750.1250.1600.2000.2500.315
20.1320.1700.2120.2650.335
2.50.1400.1800.2240.2800.355
22.4      45      10.1060.1320.1700.212N/A
1.50.1250.1600.2000.2500.315
20.1400.1800.2240.2800.355
30.1700.2120.2650.3350.425
3.50.1800.2240.2800.3550.450
40.1900.2360.3000.3750.475
4.50.2000.2500.3150.4000.500
45      90      1.50.1320.1700.2120.2650.335
20.1500.1900.2360.3000.375
30.1800.2240.2800.3550.450
40.2000.2500.3150.4000.500
50.2120.2650.3350.4250.530
5.50.2240.2800.3550.4500.560
60.2360.3000.3750.4750.600
90   180   20.1600.2000.2500.3150.400
30.1900.2360.3000.3750.475
40.2120.2650.3350.4250.530
60.2500.3150.4000.5000.630
180  355  30.2120.2650.3350.4250.530
40.2360.3000.3750.4750.600
60.2650.3350.4250.5300.670

Table 5: Pitch Diameter Tolerance for External Metric Threads (Td2)
Basic Major DiameterPitch Tolerance Grade
OverUp to and Including3456789
1.5    2.8    0.20.0250.0320.0400.050N/AN/AN/A
0.250.0280.0360.0450.056N/AN/AN/A
0.350.0320.0400.0500.0630.080N/AN/A
0.40.0340.0420.0530.0670.085N/AN/A
0.450.0360.0450.0560.0710.090N/AN/A
2.8     5.6     0.350.0340.0420.0530.0670.085N/AN/A
0.50.0380.0480.0600.0750.095N/AN/A
0.60.0420.0530.0670.0850.106N/AN/A
0.70.0450.0560.0710.0900.112N/AN/A
0.750.0450.0560.0710.0900.112N/AN/A
0.80.0480.0600.0750.0950.1180.1500.190
5.6   11.2   0.750.0500.0630.0800.1000.125N/AN/A
10.0560.0710.0900.1120.1400.1800.224
1.250.0600.0750.0950.1180.1500.1900.236
1.50.0670.0850.1060.1320.1700.2120.265
11.2     22.4     10.0600.0750.0950.1180.1500.1900.236
1.250.0670.0850.1060.1320.1700.2120.265
1.50.0710.0900.1120.1400.1800.2240.280
1.750.0750.0950.1180.1500.1900.2360.300
20.0800.1000.1250.1600.2000.2500.315
2.50.0850.1060.1320.1700.2120.2650.335
22.4      45      10.0630.0800.1000.1250.1600.2000.250
1.50.0750.0950.1180.1500.1900.2360.300
20.0850.1060.1320.1700.2120.2650.335
30.1000.1250.1600.2000.2500.3150.400
3.50.1060.1320.1700.2120.2650.3350.425
40.1120.1400.1800.2240.2800.3550.450
4.50.1180.1500.1900.2360.3000.3750.475
45      90      1.50.0800.1000.1250.1600.2000.2500.315
20.0900.1120.1400.1800.2240.2800.355
30.1060.1320.1700.2120.2650.3350.425
40.1180.1500.1900.2360.3000.3750.475
50.1250.1600.2000.2500.3150.4000.500
5.50.1320.1700.2120.2650.3350.4250.530
60.1400.1800.2240.2800.3550.4500.560
90   180   20.0950.1180.1500.1900.2360.3000.375
30.1120.1400.1800.2240.2800.3550.450
40.1250.1600.2000.2500.3150.4000.500
60.1500.1900.2360.3000.3750.4750.600
180  355  30.1250.1600.2000.2500.3150.4000.500
40.1400.1800.2240.2800.3550.4500.560
60.1600.2000.2500.3150.4000.5000.630

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