What are Standard Resistor Values?
Standard Resistor Values are the chosen values of resistance which are grouped in different series.The selection of these resistor values is depends on logarithmic sequence, which decides the placement of different resistance values in such a way that they relate with each other by tolerance.
The advantage of having Standard Resistor Values is that, every resistor manufacturers follows the standard and manufactures these values, by which these resistor values are easily available with competitive price.
Also for a circuit design while selecting a resistor, designer can get reference from list of Standard Resistor Values and choose resistance value matching to his calculated resistance value.
Generally these values are available in the resistor tolerance range of ±1%, ±2%, ±5%, ±10% and ±20%.
To know more about resistors please visit below mentioned articles;
"Resistor and Working of Resistor"
"Electrical Resistance and Resistivity".
E series of Standard Resistor Values
E series is the name of the group of series of the standard resistor values. Here in the series the values are decided such that the upper side tolerance of one resistance value should not cross the lower side tolerance of another resistance value.The standard resistor values structure is also called as EIA standard resistor values because this is approved by EIA (Electrical Industries Association).
The E series standard resistor values are globally recognized and have been accepted by all organisations who deal with international standards.
Eseries of Standard Resistor Values are published in standard IEC 60063:1963.
What is Standard Resistance?
Let understand the Standard Resistance with an example. Consider a resistor of resistance value 1Ω, which have a resistance tolerance of ±20%. This means, the minimum resistance of this resistor will be 0.2Ω and the maximum resistance of this resistor will be 1.2Ω. So, as per resistor standard values the next available resistor value after 1.2Ω will be 1.5Ω.Further same standard resistor value rule will be followed by 1.5Ω for both side i.e. minimum and maximum resistor tolerance. The minimum resistance value of 1.5Ω with ±20% resistance tolerance is 1.2Ω, which is touching the 1.2Ω value, not overlapping it.
For all the values present in the decade this process is followed and finally it creates a set of different resistance values named as Standard Resistor Values or Resistor Standard Values.
Available Resistor Values with E series
Now we know about E series of Standard Resistor Values. Each E series represents different available resistor values.
Let understand it in detail, here each set of standard resistor values have an identification number i.e. Eseries number. Here “E” is constant and “series” denotes the number i.e. 1, 3, 6, 12, 24, 48, 96 and 192.
E1 has 1 resistor values in each decade, E3 has 3 resistor values in each decade, E6 has 6 resistor values in each decade, E12 has 12 resistor values in each decade, E24 has 24 resistor values in each decade, and it continues further.
A decade of the E6 resistor values 
Resistor Tolerance with E series
E1 resistor series have very wide tolerance range and now days it didn’t exist.Further let understand the E series resistor tolerance with E3 series. As mentioned above 3 resistor values are available in E3 series these are; 1, 2.2 and 4.7. The resistor tolerance is much more than 20%. This is a basic series and rarely used now days because requirement of today’s applications need narrow resistor tolerance, but this series has wide tolerance range.
This series we can found in the application related to electrolytic capacitors where the tolerance requirement is unbalanced i.e. minimum tolerance requirement is less and maximum tolerance requirement is more or vice versa, like tolerance of 20 at minimum side and +70% at maximum side. Also, we can found these series in applications where or for components where pullup resistor value requirement are not critical.
Next is E6 series which have 6 resistor values in each decade. The resistor tolerance is ±20%.
Let see further E6 series in detail. In E6 series each decade is divided into 6 steps. The size of every step is equal to:
10E(1/6)= 1.44
Below diagram explains it in more detail;
Resistor Tolerance with E series 
E24 series have tolerance range of ±5%. E48 series have tolerance range of ±2%. E96 series have tolerance range of ±1%. E192 series have tolerance range of ≤±0.5%.
Below tables shows summary of different E series and their resistance tolerance;
E series

Available Resistor Values

Resistor Tolerance

E1

1

Very wide tolerance

E3

3

> 20%

E6

6

20%

E12

12

10%

E24

24

5% (sometimes 2% also available)

E48

48

2%

E96

96

1%

E192

192

0.5%, 0.25%, 0.1%

Below table shows list of Standard Resistor Values in tabular format;
Standard Resistor Values Table


These
values are normally available in the multiples of;
0.1,
1, 10, 100, 1k, and 1M.


E1

E3

E6

E12

E24

E48

E96

E192

E192
(cont.)

1

1

1

1

1

1

1

1

3.16


2.2

1.5

1.2

1.1

1.05

1.02

1.01

3.2


4.7

2.2

1.5

1.2

1.1

1.05

1.02

3.24



3.3

1.8

1.3

1.15

1.07

1.04

3.28



4.7

2.2

1.5

1.21

1.1

1.05

3.32



6.8

2.7

1.6

1.27

1.13

1.06

3.36




3.3

1.8

1.33

1.15

1.07

3.4




3.9

2

1.4

1.18

1.09

3.44




4.7

2.2

1.47

1.21

1.1

3.48




5.6

2.4

1.54

1.24

1.11

3.52




6.8

2.7

1.62

1.27

1.13

3.57




8.2

3

1.69

1.3

1.14

3.61





3.3

1.78

1.33

1.15

3.65





3.6

1.87

1.37

1.17

3.7





3.9

1.96

1.4

1.18

3.74





4.3

2.05

1.43

1.2

3.79





4.7

2.15

1.47

1.21

3.83





5.1

2.26

1.5

1.23

3.88





5.6

2.37

1.54

1.24

3.92





6.2

2.49

1.58

1.26

3.97





6.8

2.61

1.62

1.27

4.02





7.5

2.74

1.65

1.29

4.07





8.2

2.87

1.69

1.3

4.12





9.1

3.01

1.74

1.32

4.17






3.16

1.78

1.33

4.22






3.32

1.82

1.35

4.27






3.48

1.87

1.37

4.32






3.65

1.91

1.38

4.37






3.83

1.96

1.4

4.42






4.02

2

1.42

4.48






4.22

2.05

1.43

4.53






4.42

2.1

1.45

4.59






4.64

2.15

1.47

4.64






4.87

2.21

1.49

4.7






5.11

2.26

1.5

4.75






5.36

2.32

1.52

4.81






5.62

2.37

1.54

4.87






5.9

2.43

1.56

4.93






6.19

2.49

1.58

4.99






6.49

2.55

1.6

5.05






6.81

2.61

1.62

5.11






7.15

2.67

1.64

5.17






7.5

2.74

1.65

5.23






7.87

2.8

1.67

5.3






8.25

2.87

1.69

5.36






8.66

2.94

1.72

5.42






9.09

3.01

1.74

5.49






9.53

3.09

1.76

5.56







3.16

1.78

5.62







3.24

1.8

5.69







3.32

1.82

5.76







3.4

1.84

5.83







3.48

1.87

5.9







3.57

1.89

5.97







3.65

1.91

6.04







3.74

1.93

6.12







3.83

1.96

6.19







3.92

1.98

6.26







4.02

2

6.34







4.12

2.03

6.42







4.22

2.05

6.49







4.32

2.08

6.57







4.42

2.1

6.65







4.53

2.13

6.73







4.64

2.15

6.81







4.75

2.18

6.9







4.87

2.21

6.98







4.99

2.23

7.06







5.11

2.26

7.15







5.23

2.29

7.23







5.36

2.32

7.32







5.49

2.34

7.41







5.62

2.37

7.5







5.76

2.4

7.59







5.9

2.43

7.68







6.04

2.46

7.77







6.19

2.49

7.87







6.34

2.52

7.96







6.49

2.55

8.06







6.65

2.58

8.16







6.81

2.61

8.25







6.98

2.64

8.35







7.15

2.67

8.45







7.32

2.71

8.56







7.5

2.74

8.66







7.68

2.77

8.76







7.87

2.8

8.87







8.06

2.84

8.98







8.25

2.87

9.09







8.45

2.91

9.2







8.66

2.94

9.31







8.87

2.98

9.42







9.09

3.01

9.53







9.31

3.05

9.65







9.53

3.09

9.76







9.76

3.12

9.88

Prepared by; www.powerelectronicstalks.com

Now days in many datasheets we can see the resistor series is mentioned like; E96 + E24 and E192 + E24 i.e. addition of two E series. To meet market requirement this is purposely done by resistor manufacturers as some resistor values in E24 series are not available in E48, E96 and E192 series. So, to get lower tolerance values like; 1%, 0.5%, 0.25%, 0.1% they have added values in E24 series with other series i.e. tolerances.
Standard Resistor Value Formula
Below formula is for standard resistor value calculation;R = D . 10E(I/N)
Where,
D = Decade multiplier i.e. 1, 10, 100, 1k, 10k
N = Tolerance of E series i.e. 1%, 2%, 5%, 10%, 20%
I = 0 … N1
Unit of R is Ω
E is exponent
Let understand by an example, result of a calculation is 257kΩ with the tolerance of 1%.
Check in the table and select the nearest available value i.e. 2.58. Multiply this with a multiplier of 100000 you will get 258kΩ.
Conclusion
Standard resistor values helps in many ways to both resistor manufacturers and circuit designers. The resistor manufacture can produce the resistors which are mentioned in the standard and they don’t have to produce the nonstandardized resistors and fill their inventory.While designing the circuit the design engineer can easily identify and select the resistor value by looking up in the standard resistor value list. Designers can select the value which is closely matching to their calculated value.
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