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SMD Resistor Code & Resistance Calculator

Decode 3-digit, 4-digit, and EIA-96 SMD surface mount resistor markings into exact resistance values (Ω, kΩ, MΩ).

Supports 3-digit (103), 4-digit (1002), EIA-96 (01A) and R-notation (4R7).

Resistance
10 kΩ
Exact value
10,000 Ω
Marking scheme
3-digit
±5% (E24 series, typical)

Decoding steps

First two digits are the significant figures: 10.

Third digit is the multiplier: ×10^3.

10 × 10^3 = 10000 Ω

Marking schemes

3-digit —
two significant figures, third digit is the power of ten. 103 = 10 × 10³ = 10 kΩ.
4-digit —
three significant figures, fourth is the power of ten. 1002 = 100 × 10² = 10 kΩ.
EIA-96 —
two digits index the E96 series, the letter is the multiplier. 01A = 100 × 1 = 100 Ω.
R-notation —
R marks the decimal point. 4R7 = 4.7 Ω, R47 = 0.47 Ω.

SMD Resistor Code & Resistance Calculator: how it works

Four different marking schemes appear on surface-mount resistors, and reading the wrong one gives an answer that is out by orders of magnitude.

The four schemes

SchemeExampleMeaning
3-digit103First two digits, then the power of ten: 10 × 10³ = 10 kΩ
4-digit1002First three digits, then the power: 100 × 10² = 10 kΩ
EIA-9601ATwo digits index the E96 table, letter is the multiplier: 100 × 1 = 100 Ω
R-notation4R7R marks the decimal point: 4.7 Ω

EIA-96 in detail

EIA-96 exists because a three-digit code cannot express E96 series values precisely. The two digits are a position in a 96-value lookup table, and the letter gives the multiplier.

LetterMultiplier
Z0.001
Y or R0.01
X or S0.1
A1
B or H10
C100
D1000
E10000
F100000

Worked example · Decoding 68C

Given

  • Code: 68C

Working

  1. 1Position 68 in the E96 table = 499
  2. 2Letter C = multiplier 100
  3. 3499 × 100 = 49,900

49.9 kΩ, ±1 percent

Reading small packages

  • 0805 and larger are usually marked; 0603 sometimes; 0402 and smaller are typically unmarked.
  • A single 0 or 000 indicates a zero-ohm link, used as a jumper.
  • Unmarked resistors must be measured, or identified from the board’s bill of materials.
  • Tolerance is not marked on the component; 3-digit codes are usually 5 percent and 4-digit or EIA-96 are 1 percent.

Frequently asked questions

Three digits: first two are significant, third is the power of ten. Four digits: first three significant, fourth is the power. Two digits and a letter is EIA-96. Any R marks a decimal point.

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