Learn Resistor value and Colour Codes

SMD Resistor: Surface Mount Technology

SMD Resistor stands for “Surface Mount device” (Taken out from SMT = Surface Mount Technology) Resistor. These tiny chips are marked with three (3) or four (4) digit codes which are called SMD Resistor codes to indicate their resistance values.

Below are some given roles which help to know the exact value of an SMD resistor by seeing the printed character codes on those tiny chips.

Reading 3-Digit SMD Resistor Codes

• The first two (2) digits or numbers will indicate the significant digits or numbers.
• The third one will be a multiplier (in Power of Ten i.e. 10^ something) and then must be multiplied by the first two (2) significant digits or numbers or the third one will indicate how many Zeros should be added to the first two (2) significant digits or number.
• The letter “R” is used for Decimal Point “.” i.e. 1.1 Ω = 1R1 Ω
• Resistances below 10 ohms (Ω) do not have a multiplier.

Examples of 3-Digit SMD Resistor Codes

250 = 25 x 10⁰ = 25 x 1 = 25 Ω (This is only and only 25Ω not 250 Ω)

100 = 10 x 10⁰ = 10 x 1 = 10 Ω

721 = 72 x 10¹ = 72 x 10 = 720 Ω

102 = 10 × 10² =10 x 100 = 1000Ω or 1kΩ 915 = 91 x 10⁵ = 91 x 100000 = 9,100,000 Ω = 9.1MΩ

4R7 = 4.7Ω

R12 = 0.12 Ω

Reading 4-Digit SMD Resistor Codes

There is nothing new but the same method to read the value of SMD resistors as mentioned above for the 3 digits SMD roosters. The only difference is that with the significant numbers. In short, in the above method, the first two digits indicate significant numbers while in this method, the first three digits or numbers will show the significant numbers. Let’s see how to do it.

• The first three (3) digits or numbers will indicate the significant digits or numbers.
• The fourth one will be a multiplier (in Power of Ten i.e. 10^ something) and then must be multiplied by the first two (3) significant digits or numbers or the fourth one will indicate how many Zeros should be added to the first two (2) significant digits or number.
• The letter “R” is used for Decimal Point “.” i.e. 11.5 Ω = 11R5 Ω (4-digit SMD resistors (E96 series).
• Resistances below 10 ohms (Ω) do not have a multiplier.

Examples of 4-Digit SMD Resistor Codes

2500 = 250 x 10⁰ = 250 x 1 = 250 Ω (This is only and only 250Ω not 2500 Ω)

1000 = 100 x 10⁰ = 100x 1 = 100 Ω

7201 = 720 x 10¹ = 720 x 10 = 7200 Ω or 7.2kΩ

1001 = 100 × 10¹ =100 x 10 = 1000 Ω or 1kΩ

1004 = 100 × 10⁴ =100 x 10000 = 1000,000 Ω or 1MΩ

R102 = 0.102 Ω (4-digit SMD resistors (E96 series)

0R10 = 0.1 x 10⁰ = 0.1 x 1 = 0.1 Ω (4-digit SMD resistors (E24 series)

25R5 = 25.5Ω (4-digit SMD resistors (E96 series))

Reading EIA-96 SMD Resistor Codes

EIA-96 SMD Resistor Codes marking method is a new method that appeared on 1% of all SMD resistors. It consists of 3- Character codes.

Below are the rules to follow to know the value of EIA-96 SMD resistors.

• The first two (2) digits or numbers will indicate the significant digits or numbers
• The third one “Letter” is a multiplier (in Power of Ten i.e. 10^ something) and then must be multiplied by the first two (2) significant digits.
•  Must follow the codes in Tables (1) and (2).

Below is the table (1) to show the multiplier values of different Letters using the EIA-96 coding system for SMD Resistor Codes.

Table (1)

Also, look at the examples of reading EIA-96 SMD Resistor Codes for the importance of the use of a table (2)

Table (2)

Examples of EIA-96 SMD Resistor Codes

• 01F =     10M
• 01E =     1MΩ
• 01C=     10kΩ
• 01B =   1kΩ
• 01A =   100Ω
• 01X =   10Ω
• 01Y =   1Ω
• 66X = 475 x 0.1 = 47.5 …→ (in table (2), 66 = 475 and in table (1), X = 0.1. so 475 x 0.1 = 47.1Ω)
• 85Z = 750 x 0.001 = 0.75Ω → (in table (2), 85 = 750 and in table (1), Z = 0.001. so 750 x 0.001 = 0.75Ω)
• 36H = 232 x10 = 2320Ω = 2.32kΩ → (in table (2), 36 = 232 and in table (1), H = 10. so 232 x 10= 2.32kΩ)