SMD Resistor Code Calculator

About the SMD Resistor Code Calculator

Surface-mount resistors are printed with a short code instead of colour bands. Type the code from the part and the calculator reads it in every scheme it could belong to: 3-digit codes such as 472 (47 × 10² = 4.7 kΩ), 4-digit codes such as 4701, codes with R as the decimal point (4R7 = 4.7 Ω, R010 = 10 mΩ) or L/m for milliohms, and the three-character EIA-96 codes of 1% parts, such as 01C (10 kΩ) and 68X (49.9 Ω).

It works the other way too: enter a value and get its 3-digit, 4-digit and EIA-96 codes. Both directions say whether the value exists in the E24 (±5%) and E96 (±1%) series — the values chip resistors are actually made in. Codes whose letters manufacturers use differently, such as R and S in EIA-96, get every reading, so you can check against the datasheet.

The marking schemes

• 3 digits: two significant digits and the number of zeros — 103 = 10 × 10³ = 10 kΩ, 100 = 10 Ω. Used for E24 (±5%) parts.
• 4 digits: three significant digits and the number of zeros — 1002 = 10.0 kΩ, 4992 = 49.9 kΩ. Used for precision (±1%) parts of size 0805 and larger.
• R, L/m, K, M as the decimal point (the RKM code of IEC 60062): 4R7 = 4.7 Ω, R470 = 0.47 Ω, 10R0 = 10.0 Ω; L (in IEC 60062) or m marks milliohms, 4L7 = 4m7 = 4.7 mΩ.
• EIA-96: two digits give the position of the value in the E96 series (01 = 100, 02 = 102 … 96 = 976) and a letter the multiplier — Z ×0.001, Y ×0.01, X ×0.1, A ×1, B ×10, C ×100, D ×1000, E ×10⁴, F ×10⁵. Used on small 1% parts (0603), where four digits do not fit.
• 0 or 000: a zero-ohm link.

Many 0402 and smaller resistors carry no marking at all.

Letters that makers use differently

The EIA-96 letters A–F, X, Y and Z are used the same way everywhere, but published charts disagree on the extra letters: some list R as ×0.01 and S as ×0.1, others the other way round, and Bourns uses G for ×10⁶ and H for ×10⁷ where older charts have H = ×10. A trailing R can also be the RKM decimal point (47R = 47 Ω). For these codes the calculator lists every reading — the part’s size and the maker’s datasheet decide.

Standard values: E24 and E96

Chip resistors are made in the preferred values of IEC 60063: E24 for ±5% parts (10, 11, 12, 13, 15 … 91) and E96 for ±1% parts (100, 102, 105 … 976), in every decade. A value that is in neither — say 4.8 kΩ — is very unlikely on a real part, so check for a misread character. Some makers also sell E24 values at ±1%; Stackpole, for example, underlines a 3-digit code to show ±1% on parts dated from April 2025.

Sources

• IEC 60062:2016+AMD1:2019, Marking codes for resistors and capacitors (RKM code and the three-character E96 code)
• IEC 60063:2015, Preferred number series for resistors and capacitors
• Bourns, CR Series — Thick Film Chip Resistors datasheet (marking: E-24 3 digits, E-96 4 digits, EIA-96 on 0603, multiplier letters)
• Stackpole Electronics, RMCF/RMCP Series datasheet, part marking specifications

Limitations

• Some manufacturers use their own markings (letters, logos, colour dots or date codes). If a code does not decode sensibly, look up the part number on the reel or in the datasheet.
• Tolerance is not part of most codes; the “usually” notes describe common practice, not a guarantee.
• Codes with the letters R, S, H or G after two digits have more than one reading. The size of the part (EIA-96 is used on 0603) and the datasheet tell you which is meant.

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