SMD Resistor Codes: How to Read 103, 4R7 and EIA-96 (01C)

Chip resistors are the most common part on almost any board you open. Instead of colour bands they carry a short code of three or four characters — and on the smallest cases, nothing at all. This page walks through the standard marking systems (IEC 60062 and EIA) with worked examples, gives the complete EIA-96 table, and explains what to do when the marking is gone. Capacitors follow different rules; see SMD capacitor markings.

Case sizes and typical power

The case size is four digits: length and width. Most catalogues use inch codes, so 0805 means 0.08 × 0.05 in. Some use metric codes, and that is where mistakes happen: metric 0603 is the tiny inch 0201 (0.6 × 0.3 mm), while the familiar inch 0603 is metric 1608. Check which system a distributor uses before you order.

Inch	Metric	Size, mm	Typical power
0201	0603	0.6 × 0.3	1/20 W
0402	1005	1.0 × 0.5	1/16 W
0603	1608	1.6 × 0.8	1/10 W
0805	2012	2.0 × 1.25	1/8 W
1206	3216	3.1 × 1.55	1/4 W
2010	5025	5.0 × 2.5	1/2 W and up
2512	6432	6.3 × 3.2	1 W

These are typical ratings at 70 °C for standard thick-film parts (Bourns CR and Yageo RC datasheets). High-power series exist in the same cases, so always take the figure from the datasheet of the actual part. Don't drop a smaller case into a larger footprint just because the value matches — it dissipates less heat.

0201 and 0402 parts are usually unmarked. 0603 parts mostly carry three characters, 0805 and larger three or four.

Three-digit code: 103, 472, 330

Used on 5 % resistors (E24 series). The first two digits are significant, the third is the number of zeros to add — the power of ten. The result is in ohms.

• 103 = 10 × 10³ = 10 kΩ
• 472 = 47 × 10² = 4.7 kΩ
• 101 = 100 Ω
• 224 = 220 kΩ
• 105 = 1 MΩ
• 330 = 33 Ω, not 330 Ω — a trailing zero means “add no zeros”.

Some makers put a short bar under a three-digit code on 0603 parts to mark a 1 % E24 value (Yageo does this). Read the value the usual way.

Four-digit code: 4702, 1002, 3160

Precision resistors (1 % and better) need three significant digits, so the code grows to four characters: three significant digits plus the number of zeros.

• 4702 = 470 × 10² = 47 kΩ
• 1002 = 10 kΩ
• 1001 = 1 kΩ
• 4422 = 44.2 kΩ
• 3160 = 316 Ω

Watch out: 1000 is 100 Ω, and 1002 (10 kΩ) is not the same part as 102 (1 kΩ).

R as the decimal point

Values below 10 Ω (below 100 Ω in the four-digit code) use the letter R where the decimal point would be. There is no multiplier; what you read is the value in ohms.

• 4R7 = 4.7 Ω, 2R2 = 2.2 Ω, 1R0 = 1 Ω
• R47 = 0.47 Ω, R10 = 0.1 Ω
• 31R6 = 31.6 Ω

Milliohm current-sense resistors

Shunts in power supplies, chargers and battery management boards are in the milliohm range. They use the same R (R020 = 20 mΩ) or, in some series, a lower-case m as the decimal point: 1m5 = 1.5 mΩ (Yageo PR and PA series). If a shunt carries a code you don't recognise, look up the series datasheet rather than guessing.

EIA-96: two digits and a letter (01C, 68X)

Four characters don't fit on an 0603 case, so 1 % E96 values there use the EIA-96 code. The two digits are not the value but its index in the E96 series (01 to 96); the letter is the multiplier. Look the index up in the table below and multiply.

• 01C = 100 × 10² = 10 kΩ
• 10C = 124 × 10² = 12.4 kΩ
• 09B = 121 × 10 = 1.21 kΩ
• 88A = 806 Ω
• 68X = 499 × 0.1 = 49.9 Ω

Multiplier letters

Letter	Multiplier	Letter	Multiplier
Z	× 0.001	C	× 100
Y	× 0.01	D	× 1,000
X	× 0.1	E	× 10,000
A	× 1	F	× 100,000
B	× 10

These letters agree across manufacturer datasheets and reference charts. R, S and H do not: some tables give R = × 0.01 and S = × 0.1, others the reverse, and H appears both as × 10 and as × 10⁷. If you meet one of those, measure the part or find the datasheet. Also note that F here is a multiplier, not the 1 % tolerance letter used in part numbers.

EIA-96 code 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

Zero-ohm jumpers: 0 or 000

A resistor marked 0 (on some parts 000 or 0000, depending on the case) is a jumper — a conductor in a resistor package, used to hop over a trace or to select a circuit option at assembly. Its resistance is not exactly zero but up to a few tens of milliohms (max. 50 mΩ for the Bourns CR series), and it has a current rating in the datasheet. Replace it with the same part. If one has burnt, find the short downstream first, or the new one will go the same way.

Resistor or inductor?

A dark block marked 4R7, 100 or 101 may be an SMD power inductor. On those the code is inductance in microhenries, read by the same rule: 4R7 = 4.7 µH, 100 = 10 µH, 101 = 100 µH (TDK, Würth Elektronik, Jauch). Ways to tell them apart:

• Look: a resistor is flat, with a white ceramic underside and metal end caps; an inductor is thicker, often square, made of grey or black ferrite, sometimes with the winding visible.
• Position: next to a switching regulator IC and its output capacitors, it is most likely an inductor.
• Ohmmeter: a 4.7 µH inductor reads close to zero, a 4R7 resistor about 4.7 Ω.

More on this in SMD inductor markings.

Checking a resistor on the board

1. Power the board down and discharge the large capacitors.
2. Measure in circuit. Parallel paths can only lower the reading, so a value clearly above nominal — or an open circuit — means the resistor is bad.
3. A reading below nominal proves nothing yet: other parts, IC junctions or capacitors charging from the meter may sit in parallel. Swap the probes; if the number changes, there is a semiconductor in parallel.
4. To be sure, lift one end and measure again.
5. For low values, short the probes first and subtract the lead resistance. A milliohm shunt is beyond a normal multimeter — you need a four-wire (Kelvin) measurement.

When there is no marking (0402 and smaller) or it has burnt off, take the value from the schematic or boardview, from an identical working board, or from an identical channel on the same board, and measure the removed part on its own.

Common mistakes

• Reading 330 as 330 Ω — it is 33 Ω.
• Mixing up 4R7 (4.7 Ω), 470 (47 Ω) and 471 (470 Ω).
• Reading an EIA-96 code as a plain number: 01C is 10 kΩ. Two digits and a letter always mean the table.
• Confusing inch and metric case codes when ordering.
• Fitting a smaller case than the original — it may not handle the power.
• Replacing a resistor only because it “reads low” in circuit without checking what is in parallel.
• Taking an inductor for a resistor, or the other way round.

In short

• Three digits: two significant digits plus the number of zeros — 103 = 10 kΩ.
• Four digits: three significant digits plus the number of zeros — 4702 = 47 kΩ.
• R is the decimal point: 4R7 = 4.7 Ω; on shunts m is the decimal point in milliohms.
• Two digits and a letter — EIA-96: table value × multiplier, 01C = 10 kΩ.
• 0 or 000 is a jumper.
• In circuit a resistor can read low, but never high.

If you track repairs in ServiceCenterSoft, a resistor taken from stock goes onto the repair estimate as a line and comes off the stock balance. Stock is kept as a journal of receipts and write-offs, and for parts you use a lot you can set a minimum quantity, so they show up under “running low”. See spare parts tracking.