Calculators
SMD resistor code calculator
By Bulan Sarkar
Type the code printed on a chip resistor to get its value, or type a value to see every code it can carry. It reads three-digit, four-digit, R-for-decimal-point and EIA-96 markings, and says so when a code cannot exist or could be read two ways.
Three or four characters: 103, 4702, 4R7, R047, 01C.
- Resistance
- 47 kΩ
- Code system
- four-digit code
- Usual grade
- ±1 %
- four-digit codes usually go on ±1 % parts
How it reads: 470 × 10² = 47 kΩ.
Count the characters first
Three digits means two figures and a count of zeros: 103 is 10 followed by three zeros, 10 kΩ. Four digits means three figures and a count of zeros: 1002 is 100 followed by two zeros, also 10 kΩ. The extra figure is there because the part is made to a tighter tolerance, usually ±1 %, and needs the third figure to name its value. An R stands where the decimal point goes, so 4R7 is 4.7 Ω and R047 is 0.047 Ω. A part printed 0 or 000 is a zero-ohm link.
Two digits and a letter is EIA-96, and the digits are not the value. They are a position in the E96 table of 96 preferred values, and the letter is the multiplier. 01C is entry 1, which is 100, times 100 for C: 10 kΩ. 24C is entry 24, 174, times 100: 17.4 kΩ. The SMD resistor codes lesson explains why the scheme spends a character on a table index, and the E-series lesson covers the table itself.
The calculator checks what you type against these rules. An EIA-96 index above 96, a multiplier letter that no data sheet uses, a three-digit code starting with 0 or a multiplier that would put the part above anything made in chip form all get a message rather than a wrong number. Some characters also read two ways: 10R is 10 Ω written with R for the decimal point, but on a code chart that uses R for ×0.01 it would be EIA-96, 1.24 Ω. The calculator shows the likely reading and says what the other one would be.
Worked examples
Two reels: 473 and 4702
473 is 47 followed by three zeros, 47 kΩ. 4702 is 470 followed by two zeros, 47 kΩ. The resistance is the same. The four-digit part is usually the tighter grade, so it can stand in for the three-digit one, but the swap the other way needs a look at the tolerance first.
Add one character to the first code and the answer moves a long way. 4730 is a four-digit code, 473 followed by no zeros: 473 Ω, about a hundredth of the value. Both fit the same footprint, which is why it pays to count characters before reading them.
Coding 4.99 kΩ, a ±1 % value
4.99 kΩ has three figures. The three-digit code only has room for two, so the nearest it can print is 502, which marks 5 kΩ, +0.2 % away. That is a different resistor, so a 4.99 kΩ part needs a longer code.
The four-digit code has room: 499 followed by one zero, 4991. In EIA-96, 499 is entry 68 of the E96 table and B multiplies by 10, so the same part may instead read 68B. Both mark 4.99 kΩ.
The EIA-96 table
Index and the three figures it stands for, followed by the multiplier letters. Checked against the Yageo chip-resistor marking data sheet and the Bourns CRP0603 data sheet, which print the same table.
| Code | Value | Code | Value | Code | Value | Code | Value | Code | Value | Code | Value | Code | Value | Code | Value |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 01 | 100 | 13 | 133 | 25 | 178 | 37 | 237 | 49 | 316 | 61 | 422 | 73 | 562 | 85 | 750 |
| 02 | 102 | 14 | 137 | 26 | 182 | 38 | 243 | 50 | 324 | 62 | 432 | 74 | 576 | 86 | 768 |
| 03 | 105 | 15 | 140 | 27 | 187 | 39 | 249 | 51 | 332 | 63 | 442 | 75 | 590 | 87 | 787 |
| 04 | 107 | 16 | 143 | 28 | 191 | 40 | 255 | 52 | 340 | 64 | 453 | 76 | 604 | 88 | 806 |
| 05 | 110 | 17 | 147 | 29 | 196 | 41 | 261 | 53 | 348 | 65 | 464 | 77 | 619 | 89 | 825 |
| 06 | 113 | 18 | 150 | 30 | 200 | 42 | 267 | 54 | 357 | 66 | 475 | 78 | 634 | 90 | 845 |
| 07 | 115 | 19 | 154 | 31 | 205 | 43 | 274 | 55 | 365 | 67 | 487 | 79 | 649 | 91 | 866 |
| 08 | 118 | 20 | 158 | 32 | 210 | 44 | 280 | 56 | 374 | 68 | 499 | 80 | 665 | 92 | 887 |
| 09 | 121 | 21 | 162 | 33 | 215 | 45 | 287 | 57 | 383 | 69 | 511 | 81 | 681 | 93 | 909 |
| 10 | 124 | 22 | 165 | 34 | 221 | 46 | 294 | 58 | 392 | 70 | 523 | 82 | 698 | 94 | 931 |
| 11 | 127 | 23 | 169 | 35 | 226 | 47 | 301 | 59 | 402 | 71 | 536 | 83 | 715 | 95 | 953 |
| 12 | 130 | 24 | 174 | 36 | 232 | 48 | 309 | 60 | 412 | 72 | 549 | 84 | 732 | 96 | 976 |
| Y | × 0.01 |
|---|---|
| X | × 0.1 |
| A | × 1 |
| B | × 10 |
| C | × 100 |
| D | × 1,000 |
| E | × 10,000 |
| F | × 100,000 |
Many code charts also list R, S and H as stand-ins for Y, X and B, and Z for ×0.001. Neither data sheet uses them. The calculator decodes them with a note.
What the code does not tell you
None of these codes carries the power rating, the temperature coefficient or whether the part is thick film or thin film. The package size gives a rough idea of the power, and the SMD packages lesson gives typical figures. The smallest packages, 0402 and below, often carry no marking at all. When a code is scorched or half gone, lift one end and measure it; the tolerance lesson tells you how far from the marked value a good part may read. Through-hole parts use colour bands instead, and capacitors have their own codes.