SMD resistor code calculator

This simple calculator will help you determine the value of any SMD resistor. To get started, input the 3 or 4 digit code and hit the “Calculate” button or Enter.

Note: The program was tested rigorously, but it still may have a few bugs. So, when in doubt (and when it’s possible) don’t hesitate to use a multimeter to double-check the critical components.

See also the color code calculator on this page for MELF and standard through-hole resistors.

How to calculate the value of an SMD resistor

Most chip resistors are marked with a 3-digit or 4-digit code — the numerical equivalent of the familiar color code for through-hole components. Recently, a new coding system (the EIA-96) has appeared on precision SMDs.

The 3-digit code

Standard-tolerance SMD resistors are marked with a simple 3-digit code. The first two numbers will indicate the significant digits, and the third will be the multiplier, telling you the power of ten to which the two significant digits must be multiplied (or how many zeros to add). Resistances of less than 10 ohms do not have a multiplier, the letter ‘R’ is used instead to indicate the position of the decimal point.

3-digit code examples:

220 = 22 × 100 (1) = 22Ω (not 220Ω!)
471 = 47 × 101 (10) = 470Ω
102 = 10 × 102 (100) = 1000Ω or 1kΩ
3R3 = 3.3Ω

more 3-digit SMD resistor examples…

The 4-digit code

The 4-digit code is used for marking precision surface mount resistors. It’s similar to the previous system, the only difference is the number of significant digits: the first three numberswill tell us the significant digits, and the fourth will be the multiplier, indicating the power of ten to which the three significant digits must be multiplied (or how many zeros to add). Resistances of less than 100 ohms are marked with the help of the letter ‘R’, indicating the position of the decimal point.

4-digit code examples:

4700 = 470 × 100 (1) = 470Ω (not 4700Ω!)
2001 = 200 × 101 (10) = 2000Ω or 2kΩ
1002 = 100 × 102 (100) = 10000Ω or 10kΩ
15R0 = 15.0Ω

more 4-digit SMD resistor examples…

EIA-96

Recently, a new coding system (EIA-96) has appeared on 1% SMD resistors. It consists of a three character code: the first 2 numbers will tell us the 3 significant digits of the resistor value (see the lookup table below) and the third marking (a letter) will indicate the multiplier.

Code Multiplier
Z 0.001
Y or R 0.01
X or S 0.1
A 1
B or H 10
C 100
D 1000
E 10000
F 100000

EIA-96 code examples:

01Y = 100 × 0.01 = 1Ω
68X = 499 × 0.1 = 49.9Ω
76X = 604 × 0.1 = 60.4Ω
01A = 100 × 1 = 100Ω
29B = 196 × 10 = 1.96kΩ
01C = 100 × 100 = 10kΩ

more EIA-96 SMD examples…

Code Value Code Value Code Value Code Value
01 100 25 178 49 316 73 562
02 102 26 182 50 324 74 576
03 105 27 187 51 332 75 590
04 107 28 191 52 340 76 604
05 110 29 196 53 348 77 619
06 113 30 200 54 357 78 634
07 115 31 205 55 365 79 649
08 118 32 210 56 374 80 665
09 121 33 215 57 383 81 681
10 124 34 221 58 392 82 698
11 127 35 226 59 402 83 715
12 130 36 232 60 412 84 732
13 133 37 237 61 422 85 750
14 137 38 243 62 432 86 768
15 140 39 249 63 442 87 787
16 143 40 255 64 453 88 806
17 147 41 261 65 464 89 825
18 150 42 267 66 475 90 845
19 154 43 274 67 487 91 866
20 158 44 280 68 499 92 887
21 162 45 287 69 511 93 909
22 165 46 294 70 523 94 931
23 169 47 301 71 536 95 953
24 174 48 309 72 549 96 976

Notes:

  • an SMD resistor with a marking of 0, 00, 000 or 0000 is a jumper (a zero-ohm link).
  • a chip resistor marked with the standard 3 digit code and a short bar below the marking denotes a precision (1% or less) resistor with a value taken from the E24 series (these values are usually reserved for 5% resistors). For example: 122 = 1.2kΩ 1%. Some manufacturers underline all three digits — do not confuse this with the code used on low value current sensing resistors.
  • SMDs with values in order of milliohms, made for current sensing applications are often marked with the help of the letter M or m, showing the decimal point location (with the value in milliohms). For example: 1M50 = 1.50mΩ, 2M2 = 2.2mΩ.
  • Current sensing SMDs can also be marked with a long bar on top (1m5 = 1.5mΩ, R001 = 1mΩ, etc.) or a long bar under the code (101 = 0.101Ω, 047 = 0.047Ω). The underline is used when the starting ‘R’ has to be omitted due to the limited space on the resistor’s body. So, for example, R068 becomes 068 = 0.068Ω (68mΩ).

Power rating

To find out the approximative power rating of your SMD resistor, measure its length and width. A few commonly used package dimensions with the corresponding typical power ratings are presented in the table below. Use this table as a guide only, and always consult the component’s datasheet for the exact value.

SMD resistor dimensions
Package Size in inches (L×W) Size in mm (L×W) Power rating
0201 0.024″ × 0.012″ 0.6 mm × 0.3 mm 1/20W
0402 0.04″ × 0.02″ 1.0 mm × 0.5 mm 1/16W
0603 0.063″ × 0.031″ 1.6 mm × 0.8 mm 1/16W
0805 0.08″ × 0.05″ 2.0 mm × 1.25 mm 1/10W
1206 0.126″ × 0.063″ 3.2 mm × 1.6 mm 1/8W
1210 0.126″ × 0.10″ 3.2 mm × 2.5 mm 1/4W
1812 0.18″ × 0.12″ 4.5 mm x 3.2 mm 1/3W
2010 0.20″ × 0.10″ 5.0 mm × 2.5 mm 1/2W
2512 0.25″ × 0.12″ 6.35 mm × 3.2 mm 1W

Tolerance

The standard 3 and 4 digit code does not give us a way to determine the SMD resistor’s tolerance.

In most cases, however, you’ll find that a surface mount resistor marked with the 3-digit codehas a tolerance of 5% and a resistor marked with 4-digit code or the new EIA-96 code has a tolerance of 1% or less.

There are many exceptions to this rule, so always check the manufacturer’s datasheet, especially if the component’s tolerance is critical for your application.

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