SMD Resistor Code Calculator

SMD Resistor Code Calculator Overview

The SMD Resistor Code Calculator helps you decode the resistance value printed on a surface-mount resistor. It supports the common 3-digit code, 4-digit code, and EIA-96 code used on many chip resistors.

Enter the component marking and choose the correct code format. The calculator converts the marking to a resistance value in ohms, kilohms, or megohms. This is useful when checking a loose SMD resistor, verifying a PCB assembly, or identifying a value on a component too small to use a through-hole color band code.

What Is an SMD Resistor?

An SMD resistor, or surface-mount resistor, is a small resistor designed to be soldered directly onto pads on a printed circuit board. Instead of long leads, it has metalized end terminals. Because the package is small, the resistance value is usually printed as a compact numeric or alphanumeric code.

Not every SMD resistor has a visible marking. Very small packages, special precision parts, high-volume custom parts, and some zero-ohm jumpers may be unmarked or may use a manufacturer-specific code. If the marking is missing or unclear, check the bill of materials, schematic, or manufacturer datasheet, or measure the part with a suitable meter after accounting for in-circuit paths.

SMD Resistor Code Types

Code Type	Typical Use	How It Works	Example
3-digit code	Common for E24 values and general-purpose chip resistors.	First two digits are significant figures. Third digit is the power-of-ten multiplier.	472 = 47 × 10² = 4.7 kΩ
4-digit code	Common for tighter-tolerance values where three significant digits are useful.	First three digits are significant figures. Fourth digit is the power-of-ten multiplier.	1002 = 100 × 10² = 10 kΩ
R decimal code	Low-value resistors where the decimal point must be shown.	The letter R marks the decimal point.	3R3 = 3.3 Ω
EIA-96 code	Often used on 1% precision chip resistors, especially small packages.	First two digits select a value from the E96 table. The letter gives the multiplier.	56B = 374 × 10 = 3.74 kΩ

How to Read a 3-Digit SMD Resistor Code

In a 3-digit code, the first two digits are the significant figures, and the third digit tells how many zeros to add. Equivalently, multiply the first two digits by 10 raised to the value of the third digit.

Resistance = first two digits × 10 third digit

Marking	Calculation	Resistance
220	22 × 10⁰	22 Ω
471	47 × 10¹	470 Ω
102	10 × 10²	1 kΩ
105	10 × 10⁵	1 MΩ
3R3	R is the decimal point	3.3 Ω
R47	R is the decimal point	0.47 Ω

A common mistake is reading 100 as 100 Ω. In the 3-digit system, 100 = 10 × 10⁰ = 10 Ω. A 100 Ω resistor would normally be marked 101.

How to Read a 4-Digit SMD Resistor Code

In a 4-digit code, the first three digits are the significant figures, and the fourth digit is the multiplier. This gives one more significant digit than the 3-digit code.

Resistance = first three digits × 10 fourth digit

Marking	Calculation	Resistance
4700	470 × 10⁰	470 Ω
2001	200 × 10¹	2 kΩ
1002	100 × 10²	10 kΩ
7992	799 × 10²	79.9 kΩ
15R0	R is the decimal point	15.0 Ω
0R10	R is the decimal point	0.10 Ω

How to Read an EIA-96 SMD Resistor Code

The EIA-96 marking system uses three characters. The first two characters are numbers from 01 to 96. These numbers do not directly indicate the resistance value; they identify an entry in the E96 lookup table. The third character is a letter multiplier.

Resistance = E96 table value × letter multiplier

Letter	Multiplier	Example Meaning
Y	0.01	100Y = 1.00 Ω is represented by code 01Y, because 01 = 100.
X	0.1	66X = 47.5 Ω, because 66 = 475.
A	1	01A = 100 Ω.
B	10	56B = 3.74 kΩ, because 56 = 374.
C	100	38C = 24.3 kΩ, because 38 = 243.
D	1000	39D = 249 kΩ, because 39 = 249.
E	10000	01E = 1 MΩ.
F	100000	01F = 10 MΩ.

Some manufacturers use additional or alternative letter conventions for special ranges, so always check the resistor datasheet when the marking does not match the common table.

EIA-96 Value Lookup Table

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

EIA-96 Examples

Marking	Lookup	Multiplier	Resistance
56B	56 = 374	B = 10	3740 Ω = 3.74 kΩ
28X	28 = 191	X = 0.1	19.1 Ω
39D	39 = 249	D = 1000	249 kΩ
85Y	85 = 750	Y = 0.01	7.5 Ω

How to Use the SMD Resistor Code Calculator

First, read the marking exactly as it appears on the resistor. Then choose whether it is a 3-digit code, 4-digit code, or EIA-96 code. If the code includes the letter R, treat R as the decimal point. If the code has two digits followed by a letter such as A, B, C, D, E, F, X, or Y, it is likely an EIA-96 marking.

After the calculator returns a value, check whether it is appropriate for the circuit. For example, a pull-up resistor, sense resistor, feedback resistor, and zero-ohm jumper may have very different expected ranges. If the calculated value does not make sense, check whether the part is still connected in-circuit, whether the marking is rotated, or whether the manufacturer uses a special code.

Common Mistakes When Reading SMD Resistor Codes

Mistake	Correct Interpretation
Reading 100 as 100 Ω	100 means 10 Ω in the 3-digit system. 101 means 100 Ω.
Treating EIA-96 digits as significant figures	In EIA-96, the first two digits are a lookup code, not the value itself.
Ignoring the R character	R marks the decimal point, so 4R7 means 4.7 Ω.
Assuming all SMD resistors are marked	Small parts may be unmarked. Use the BOM, datasheet, or measurement when needed.
Measuring in-circuit without checking parallel paths	Other components can change the measured resistance. Lift one terminal if an accurate value is required.

Zero-Ohm SMD Resistors

A marking such as 0, 00, or 000 often indicates a zero-ohm jumper rather than a precision resistor value. Zero-ohm resistors are used as PCB jumpers, configuration links, or assembly options. Their actual resistance is not exactly zero, so check the datasheet if current rating or voltage drop matters.

Video Reference

SMD Resistor Coding Explained with Examples.

FAQ

Is EIA-96 always used for 1% resistors?

No. EIA-96 is common on some 1% chip resistors, especially small packages, but many 1% resistors use 4-digit markings or no marking at all. Consult the manufacturer datasheet for the specific part series.

Why do some codes contain R?

The letter R is used as a decimal point. For example, 2R2 means 2.2 Ω, R22 means 0.22 Ω, and 10R0 means 10.0 Ω.

Can I decode every SMD resistor from the top marking?

Not always. Some markings are manufacturer-specific, some parts are unmarked, and some values may be ambiguous when the package is damaged or rotated. Use the schematic, BOM, datasheet, or measurement to confirm critical parts.

Does the code include tolerance and power rating?

Usually, no. The top marking primarily identifies resistance. Tolerance, power rating, voltage rating, temperature coefficient, and package size must be verified using the part number or datasheet.

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