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SMD Resistor and Capacitor Markings Explained

Last updated: 2026-10-04

The tiny code on top of a chip part is the first thing you look at during repair or reverse engineering. Yet the same 10 kΩ value can be printed as 103, 1002 or 01C depending on the part, and most chip capacitors carry no marking at all. This guide walks through the three resistor marking systems (3-digit, 4-digit, EIA-96), R notation, capacitor and inductor markings, and the things a marking never tells you: which size system, what power rating and what voltage rating.

The first two digits are significant figures and the last digit is the number of zeros (the power of ten). 472 is 47 followed by two zeros, 4,700 Ω = 4.7 kΩ. 105 is 10 followed by five zeros, 1 MΩ. The classic mistake is reading 100 as 100 Ω. It is 10 followed by no zeros, so 10 Ω; 100 Ω is marked 101. Likewise 220 is 22 Ω and 221 is 220 Ω.

Values below 10 Ω cannot be written with an exponent, so an R stands in for the decimal point: 4R7 is 4.7 Ω, R47 is 0.47 Ω, 1R0 is 1.0 Ω. Milliohm current-sense resistors may be marked R005 (5 mΩ) or with a manufacturer-specific code, so never finalize a low-ohm value from the marking alone; check the marking table in the datasheet.

Same rule, three significant digits. 4701 is 470 plus one zero, 4.7 kΩ. 1002 is 100 plus two zeros, 10 kΩ. 4991 is 4.99 kΩ and 1000 is 100 Ω. The system exists because 1% parts use E96 values (4.99k, 16.5k) that need three digits. With an R mixed in, 49R9 is 49.9 Ω.

An 0603 (1608 metric) chip has no room for four characters, so 1% resistors in that size are often marked with the EIA-96 code. The two digits (01 to 96) are the position in the E96 table and the letter is the multiplier. You look up the position rather than memorize it. Ones you will see a lot: 01 = 100, 30 = 200, 49 = 316, 66 = 475, 68 = 499, 96 = 976.

An EIA-96 marking also tells you the part is from a 1% family. A 10 kΩ part marked 103 and one marked 01C probably differ in precision. If you replace a divider or feedback resistor marked 01C with a 5% part marked 103, the output voltage can shift.

• MLCCs (multilayer ceramic): almost always unmarked. Printing on the fired ceramic body is generally not done, so a loose MLCC can only be identified with an LCR meter or from the original reel label. Some older parts carry a letter-digit code, but they are rare.
• Tantalum capacitors: value in a 3-digit picofarad code. 106 = 10 × 10⁶ pF = 10 µF, 476 = 47 µF, 107 = 100 µF. Voltage appears as a number or a letter code (many makers use A = 10 V, C = 16 V, D = 20 V, E = 25 V, V = 35 V, but it varies by series).
• The bar on a tantalum marks the positive (+) terminal. That is the opposite of a diode band (cathode) and of the marking on aluminum electrolytics (negative), which is why tantalums are the most frequently reversed part in hand assembly. A reversed tantalum fails short and can burn, so take extra care.
• Aluminum electrolytic (SMD can): the dark half-moon printed on top marks the negative side. Value is printed directly in microfarads, such as 47, often with a voltage letter.
• Power inductors: same 3-digit rule, in microhenries. 100 = 10 µH, 220 = 22 µH, 4R7 = 4.7 µH, R47 = 0.47 µH. Small chip inductors (0402, 0603) are usually unmarked.
• Diodes, transistors and ICs: the two- or three-character codes on SOT-23 and similar packages are manufacturer identification codes, not values you can decode by rule. Look them up with the package in an SMD marking code database or the datasheet's marking table.

A marking gives you resistance only. When choosing a replacement you still need the size code, the power rating and the maximum working voltage. The biggest trap with size codes is that imperial and metric systems share numbers, so '0603' alone does not tell you whether the part is 1.6 × 0.8 mm or 0.6 × 0.3 mm. The full conversion table is in our package size code article.

These are common figures for standard thick-film chip resistors; high-power and high-voltage series in the same size can be double or more. The rating people miss is voltage. If one 0603 resistor drops several hundred volts in a high-voltage divider, it is over its rating even though its resistance is fine. Use 1206 or larger there, or split the resistor into several in series so each one stays under its voltage rating.

A customer's board has a buck converter whose output looks suspicious. The two 0603 resistors on the feedback pin are marked 49C and 01C. Position 49 in E96 is 316 and C is ×100, so the top resistor is 31.6 kΩ; 01C is 10.0 kΩ. With a 0.8 V reference from the datasheet, Vout = 0.8 × (1 + 31.6 / 10) = 3.33 V, a correct 3.3 V rail design. If the measured output is far off, look at the regulator or the load, not the resistors. If someone had replaced the top resistor with a 333 (33 kΩ, 5%), the output would rise to 0.8 × 4.3 = 3.44 V. Reading the markings lets you catch that before you even pick up a probe.

• Reading 100 as 100 Ω. A 3-digit 100 is 10 Ω. The last digit counts zeros; it is not a digit of the value.
• Reading upside down. Chips are placed in any rotation, so text can appear inverted. 106 upside down looks like 901, and 900 Ω is not an E24 value, which tells you the orientation is wrong. Checking that the decoded value exists in an E series is the best sanity check you have.
• Treating an EIA-96 code as three digits. 01C makes no sense as a 3-digit code. If it ends in a letter, it is EIA-96.
• Expecting MLCCs to be marked. Unmarked is normal. Once loose MLCCs get mixed, only measurement can separate them, so discard or bag parts as you remove them during rework.
• Taking the tantalum bar as negative. On a tantalum the bar is positive. Cross-check against the silkscreen polarity mark.
• Measuring MLCC capacitance on the board. Parallel capacitors get measured too. MLCCs also lose a lot of capacitance under DC bias, and an LCR meter tests at a low voltage, so the reading differs from in-circuit behavior.
• Matching size but not power or voltage. Putting a 1206 of the same value in a 2512 spot cuts the power rating to a quarter.

1. Look at digit count and last character first: 3-digit, 4-digit, two digits plus a letter (EIA-96), or an R.
2. Does the decoded value exist in E24 (5%) or E96 (1%)? If not, suspect you read it upside down.
3. Match replacements on value, size (state both imperial and metric), power, maximum working voltage and tolerance.
4. Replace EIA-96-marked parts with 1% parts.
5. Track MLCC and chip inductor values by reel label or BOM, and never reuse removed parts.
6. Note in assembly instructions that polarity marks differ between tantalums, electrolytics and diodes.
7. Write BOM lines down to '10 kΩ 1% 0603 (1608 metric) 1/10 W', and specify the manufacturer part number (MPN) for precision positions.

This article summarises the working rules KEMI uses in real design and fabrication work. For production, part datasheets and fab specifications take precedence.