SMD resistor code calculator

How to use the SMD resistor code calculator

Count the characters printed on the chip, choose 3 or 4, then pick each character in order, left to right with the text the right way up. The calculator works out which marking system the part uses, gives the resistance, the tolerance that system usually means, whether the value belongs to a standard E-series, and the same value written in the other codes. Choose the package size if you know it: the result adds the power rating and checks that the marking makes sense for a part that size. A short line under a 3-digit code is a maker’s convention on some 0603 parts; switch it on if you see one.

Find the marking works the other way. Type a value (4k7, 12.4k and 0.1 all work), pick the tolerance and size, and the calculator shows the 3-digit, 4-digit and EIA-96 codes, flags values that a code can only approximate, and says which one a part of that size and tolerance normally carries.

How SMD resistor codes work

Chip resistors are too small for colour bands, so they print the value as digits. Three marking systems cover nearly every part you will meet, and one rule ties them together: the last digit is a multiplier, the number of zeros to add. A 3-digit code holds two significant figures, so 472 is 47 followed by two zeros, 4.7 kΩ. A 4-digit code holds three, so 4701 is 470 and one zero, the same 4.7 kΩ, and 1002 is 10 kΩ. Ordinary ±5 % parts use three digits; ±1 % parts need the third figure to show values such as 4.99 kΩ, which three digits round to 5 kΩ (502).

Below 10 Ω there are not enough digits, so the letter R stands for the decimal point: 4R7 is 4.7 Ω and R47 is 0.47 Ω. Four-character parts do the same below 100 Ω (10R0 = 10 Ω), and current-sense resistors take it down to milliohms: R005 is 5 mΩ. The international marking standard, IEC 60062, extends the idea with K, M and G for kilo, mega and giga, and since 2016 L for milli, so 4K7 is 4.7 kΩ. Those letter codes are common on drawings and larger parts; on chips you mostly see R.

EIA-96 codes on 1 % resistors

An 0603 chip, 1.6 mm long, has room for three characters but a 1 % value needs three significant figures and a multiplier. EIA-96 solves this with a lookup: two digits from 01 to 96 select one of the 96 values of the E96 series, and a letter supplies the multiplier. Code 01 is the first E96 value, 100; code 96 is the last, 976. With the letter C (×100), 01C is 10 kΩ and 10C, Bourns’ own example, is 12.4 kΩ. Because the code is just the position in the E96 list, a value that is not in E96 has no EIA-96 code: 4.7 kΩ is an E24 value, and the nearest E96 values are 4.64 kΩ and 4.75 kΩ, the latter being 66B.

01

100

02

102

03

105

04

107

05

110

06

113

07

115

08

118

09

121

10

124

11

127

12

130

13

133

14

137

15

140

16

143

17

147

18

150

19

154

20

158

21

162

22

165

23

169

24

174

25

178

26

182

27

187

28

191

29

196

30

200

31

205

32

210

33

215

34

221

35

226

36

232

37

237

38

243

39

249

40

255

41

261

42

267

43

274

44

280

45

287

46

294

47

301

48

309

49

316

50

324

51

332

52

340

53

348

54

357

55

365

56

374

57

383

58

392

59

402

60

412

61

422

62

432

63

442

64

453

65

464

66

475

67

487

68

499

69

511

70

523

71

536

72

549

73

562

74

576

75

590

76

604

77

619

78

634

79

649

80

665

81

681

82

698

83

715

84

732

85

750

86

768

87

787

88

806

89

825

90

845

91

866

92

887

93

909

94

931

95

953

96

976

The multiplier letters, with the range each one covers and how well it is documented:

Worked examples

Letters that mean two things

Z to F mean the same wherever they appear in the maker tables we checked (Bourns CR, TE CRGCQ, TT Electronics). Three letters do not, and the calculator shows every published reading instead of picking one:

• H. Bourns and TE define H as ×10⁷, so 01H would be 1 GΩ. TT Electronics’ marking note lists H as an alternative to B (×10), giving 1 kΩ. Both are maker documents, so the result shows both readings. A gigaohm chip resistor is very rare, which makes the ×10 reading the likelier one on a real board, but only a meter settles it.
• S. TT Electronics pairs S with Y (×0.01), so 01S is 1 Ω; charts elsewhere pair it with X (×0.1), giving 10 Ω. Again both readings are shown.
• R is first of all the decimal point. 47R is 47 Ω in R notation, the form IEC 60062 and maker datasheets use. Read as an EIA-96 letter it would be 30.1 Ω (TT pairs R with X) or 3.01 Ω (other charts pair it with Y), so the calculator reads R notation and lists the alternatives.
• G (×10⁶) is in both Bourns’ and TE’s tables, but it only marks values of 100 MΩ and more. Standard chip resistors stop at 10 MΩ for 1 % parts and around 20–22 MΩ for most 5 % lines, so a G code deserves a second look.

Package sizes, power ratings and which code goes where

Chip sizes are named by their length and width: in hundredths of an inch for the familiar imperial codes, in tenths of a millimetre for the metric ones. An 0805 is 0.08 × 0.05 in, and its metric name 2012 means 2.0 × 1.2 mm. Size limits what can be printed. Parts of 0402 and smaller are normally left blank. 0603 parts carry three characters, so 1 % values use EIA-96 there: 12.4 kΩ at 1 % is 10C on an 0603 but 1242 on a 1206. From 0805 up there is room for four digits.

Power ratings are where datasheets disagree. They are quoted at 70 °C ambient and fall to zero at the film’s maximum temperature, and each maker sets its own number for the same size. An 0805 is 0.125 W in Bourns’ CR and YAGEO’s thin-film RT series but 0.25 W in Vishay’s D/CRCW e3 and KOA’s RK73H; a 2010 is 0.5 W or 0.75 W depending on the maker. Thin-film parts are often rated lower than thick film in the larger sizes. The calculator shows the full range for the size you pick; for a design, use the rating of the exact part on your parts list, and leave margin.

Nominal dimensions come from the size codes; real parts have tolerances, so check the datasheet before drawing a footprint. * 1218 rating from one maker only. Maximum working voltage also limits high values: the voltage across the part is the lower of √(P × R) and this limit, so a 1 MΩ 0603 reaches its 75 V limit at 5.63 mW, long before its power rating.

Zero-ohm jumpers

A chip printed with a single 0 is not a resistor of zero times anything: it is a zero-ohm link, used as a bridge that a pick-and-place machine can fit, or as an option link on a board. Makers print it two ways: Bourns, and KOA on its 0603 parts, use a single 0; KOA on 0805 and larger parts, and Samsung, print 000. We found no maker that prints 00, so the calculator still reads it as a link but asks you to measure. Links have no tolerance. They are specified by a maximum resistance (at most 20 mΩ in Vishay’s D/CRCW e3 series, 50 mΩ in TE’s CRGCQ) and a maximum current that grows with size:

Common mistakes

• Reading the part upside down. Digits such as 6 and 9 swap when a chip is rotated. If a reading comes out absurd, try the other way up: 229 would be 22 GΩ, but rotated it reads 622, a plain 6.2 kΩ. The calculator checks this for you.
• Adding a zero too many. The last digit is the number of zeros, so 1000 is 100 Ω, not 1 kΩ, and 102 (1 kΩ) and 1002 (10 kΩ) differ tenfold.
• Confusing resistors with capacitors. The same three digits mean picofarads on a capacitor: 104 is 100 nF there, and most chip capacitors carry no marking at all. See the capacitor code calculator.
• Trusting a bar. A line under or over a code means different things to different makers. YAGEO uses a short bar on 0603 parts to mark an E24 value at 1 % or better; others use bars for orientation or not at all.
• Measuring in circuit. Parallel paths make a resistor read low on a meter. Lift one end, or compare with an identical board, before deciding a part has drifted.

Through-hole resistors use colour bands instead; the resistor colour code calculator reads 3 to 6 bands. Whether a value is standard comes from the IEC 60063 series, listed in full in the E-series resistor value tables. Once you know the value, the voltage divider calculator and the LED resistor calculator show what it does in a circuit.

Method and verification

The calculator classifies the marking by its pattern: zeros only (a link), two digits and a multiplier letter (EIA-96), one letter among digits (R notation or the IEC 60062 letter code), or three or four digits. It then multiplies the significant figures by the power of ten exactly, without floating-point noise. The EIA-96 table and multiplier letters come from Bourns’ CR datasheet, checked against TE’s CRGCQ datasheet and TT Electronics’ marking note, and our tests confirm that code nn is the nn-th value of the E96 series as listed in two Vishay value tables. Marking practice by size follows Bourns CR and YAGEO RT; link markings follow Bourns, KOA and Samsung; power ratings come from five makers’ datasheets, and jumper limits from Vishay.

The tests decode every worked example in those sources, round-trip every E24 value from 0.1 Ω to 91 MΩ through the 3-digit code, every E96 and E192 value through the 4-digit code and every E96 value through EIA-96, and check that rounding never moves a value by more than half a step. Letters with conflicting meanings (H, S, and R used as a multiplier) always show every published reading with a warning, never a silent answer.

Updated 2026-10-14. Found a problem? Report it and we log every fix publicly.