Standard Resistor Values (E-Series) Explained
Standard resistor values are the E-series sets that resistors are made in, determined by tolerance: E6 (±20%), E12 (±10%), E24 (±5%), and the precision E48/E96/E192 (±2%/±1%/±0.5%). The values follow roughly 10^(k/N); you pick the nearest standard to a calculated value.
Resistors are not made in every value; they are made in standard sets called the E-series. In a circuit you take the value from an Ohm's law calculation (say 3.1 kΩ) and pick the nearest standard value. Which values exist depends on the resistor's tolerance.
What is the E-series?
Each series divides one decade (a factor of ten) into equally spaced ratios; the values follow roughly 10(k/N) (N = the series number, k = 0…N−1). The tighter the tolerance, the more steps — because the tolerance bands of adjacent values must not overlap.
E6, E12 and E24 (common series)
| Series | Tolerance | Values (one decade) |
|---|---|---|
| E6 | ±20% | 10, 15, 22, 33, 47, 68 |
| E12 | ±10% | 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 |
| E24 | ±5% | E12 + 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, 91 |
These values repeat in every decade: 10, 100, 1k, 10k… So E12 has 22 Ω, 220 Ω and 2.2 kΩ alike.
Precision series: E48, E96, E192
Tighter-tolerance resistors have more steps: E48 (±2%), E96 (±1%) and E192 (±0.5%). Precision circuits (references, measurement, filters) usually use E96.
Why standard values?
Limiting production and stock to a small set of values lowers cost; combined with tolerance, these steps cover the whole range. That is why it is normal to pick the nearest standard instead of hunting for an exact "3,140 Ω" resistor.
Example: picking the nearest standard
Suppose an LED resistor calculation gives 440 Ω. The nearest E24 value is 470 Ω (a higher value, which lowers the current slightly — safe). If the calculation gave 3.1 kΩ, you would choose 3.0 kΩ or 3.3 kΩ in E24.
Use the calculator
To find the nearest standard resistor to any value, use our Standard Resistor Value Calculator.