Electronics / Parts
SMD Resistor Code Calculator (3-Digit, 4-Digit, EIA-96)
Find the resistance of a surface-mount resistor from its marking: 3-digit codes such as 472, 4-digit codes such as 1002, codes with R such as 4R7, and EIA-96 codes such as 01C.
SMD Resistor Code Calculator (3-Digit, 4-Digit, EIA-96): A 3-digit marking is two significant digits and a power of ten, so 472 is 47 × 10² = 4.7 kΩ. A 4-digit marking, used on 1% parts, has three digits and a power of ten: 1002 is 100 × 10² = 10 kΩ. R marks a decimal point, and 0, 00, or 000 is a zero-ohm jumper. EIA-96, used on the smallest 1% parts, gives a two-digit index into the E96 series and a letter multiplier: 01C is 100 × 100 = 10 kΩ. Runs 100% locally in your browser with zero server file uploads.
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Three digits are two significant digits and a power of ten (472 = 47 × 100 = 4.7 kΩ); four digits, used on 1% parts, are three digits and a power of ten (1002 = 10 kΩ). EIA-96 markings on small 1% parts use a two-digit index into the E96 series and a letter: Z × 0.001, Y or R × 0.01, X or S × 0.1, A × 1, B or H × 10, C × 100, D × 1 000, E × 10 000, F × 100 000. An underlined or barred code may mark a different scheme; check the maker's datasheet.
Examples of each scheme
472 = 4.7 kΩ, 101 = 100 Ω, and 220 = 22 Ω (the third digit 0 adds no zeros). 4701 = 4.7 kΩ and 1000 = 100 Ω. R10 = 0.1 Ω and 4R7 = 4.7 Ω. 68X = 499 × 0.1 = 49.9 Ω and 01C = 10 kΩ.
Leaded resistors use colour bands instead: read them with the resistor colour code tool.
Size and marking
The smallest packages, 0402 and below, are often left unmarked because there is no room; the value is only on the reel. Larger 0603 parts often use EIA-96, and 0805 and up usually carry 3- or 4-digit codes.
For the values the codes point to, the E96 series has 96 values per decade spaced about 2.4% apart, for 1% resistors.
How to use it
- Type the marking printed on the resistor.
- Read the resistance and which marking scheme it uses.
- For a marking that is not recognised, check the maker's datasheet.
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Frequently asked questions
What is a 103 SMD resistor?
10 × 10³ = 10 kΩ.
How do I tell a 3-digit code from EIA-96?
EIA-96 codes end in a letter, such as 01C or 68X; 3-digit codes are all digits.
Why is a code with a line under it different?
Some makers underline or bar a code to show a different scheme or to avoid reading it upside down; check their datasheet.
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