E-series resistor values: E3 to E192

What the E-series are

Resistors and capacitors are made in a limited set of preferred values, defined by IEC 60063 (edition 3.0, published in 2015). Each series is named after how many values it puts in one decade. E3, E6, E12 and E24 use two significant figures; E48, E96 and E192 use three. Any value in a series can be multiplied by a power of ten, so the E12 value 4.7 gives 4.7 Ω, 47 Ω, 470 Ω, 4.7 kΩ and so on. The series are nested: we checked that each one is every second value of the next finer series (E3 of E6, E6 of E12, E12 of E24, E48 of E96, E96 of E192), so a coarse value never disappears from a finer series of the same family.

The values are spaced by ratio, not by difference. Between 1 and 10 the E12 steps grow from 0.2 to 1.8, but each value is about 21 % bigger than the last. That is the point of the series: a resistor’s tolerance is a percentage, so equal ratios give equal coverage at every value.

Step between values = 10^(1/N) − 1. Bands meet at: the ± tolerance at which neighbouring values’ tolerance bands just touch, (r − 1)/(r + 1) with r = 10^(1/N). Usual tolerance as printed by Vishay (document 50034); E3 has none listed.

Which tolerance goes with which series

Vishay’s value table pairs E192 with ±0.5 %, E96 with ±1 %, E48 with ±2 %, E24 with ±5 %, E12 with ±10 % and E6 with ±20 %; its second table adds ±2 % for E24 and ±0.1 % and ±0.25 % for E192. The overview table shows why the pairing works. In an ideal E12 series the bands of neighbouring values would touch at ±9.6 %, so ±10 % parts overlap a little and cover the whole decade; E6 at ±20 % and E24 at ±5 % are matched the same way. The printed values are rounded, though, and that leaves a few small holes. With every value at its usual tolerance, E6 covers the decade completely (some bands only just touch); E12 misses 1.32 to 1.35 and 2.42 to 2.43; and E24 has 7 gaps, the widest from 1.365 to 1.425. In the three-figure series the usual tolerance is tighter than the point where bands meet, so narrow gaps are normal there: a precision part is meant to be close to its own value, not to cover the decade.

The pairing is a convention, not a rule. Vishay’s own thick-film chips are sold at ±1 % in both E24 and E96 values, and KEMET offers some ceramic capacitor ranges in E24 values and others in E12. What the series fixes is the set of values; the tolerance printed on the part is what you can rely on. IEC 60063:2015 also changed its guidance on relating series to tolerance, and its text is not freely available, so we quote the makers’ pairings here.

The formula: 10 to the power i over N

The ideal i-th value of a series with N values per decade is

for i = 0 to N − 1, rounded to two significant figures for E3 to E24 and to three for E48 to E192. We recomputed every series from this formula and compared it with the lists printed by Vishay. E48 and E96 match it everywhere. E192 has a single exception, 9.20 where the formula gives 9.1948, which rounds to 9.19. The two-figure series are different: E24 departs from the formula in 8 places, E12 in 5, E6 in 2 and E3 in 1. The closest call in any series is 1.694988, which rounds to 1.69 by a margin far larger than floating-point error, so these counts are exact.

Why 4.7 kΩ and not 4.6 kΩ

The formula puts the ninth E12 value (and the seventeenth E24 value) at 4.6416, which rounds to 4.6. The standard value is 4.7, +1.26 % away. IEC 60063 fixes E3 to E24 as listed rather than as calculated; the lists have been an IEC standard since at least the 1963 edition, which IEC 60062 still referenced in 2004. Because the series nest, the choice carries through: 4.7 is the third value of E3, so it is also in E6, E12 and E24. The other exceptions enter at different levels: 3.3 is an E6 value, 2.7, 3.9 and 8.2 are E12 values, and 3.0, 3.6 and 4.3 are E24 values. None is more than 4.4 % from the formula, and the tolerance bands still overlap, as the diagram above shows.

The practical consequence is that 4.6 kΩ is not a part you can buy in any series. With ±5 % parts you fit 4.7 kΩ; at ±1 % the E96 neighbours are 4.64 kΩ and 4.75 kΩ. If a design really needs 4.6 kΩ, two parts get there: 4.3 kΩ and 300 Ω in series, both E24 values, make exactly 4.6 kΩ.

For the values you meet most often, we have a page each with every marking and its uses: the 4.7 kΩ resistor, the 1 kΩ resistor, the 10 kΩ resistor and the 100 kΩ resistor.

E3, E6, E12 and E24 values

The two-figure series, as resistor values across seven decades. E12 values are in bold; the last column shows which coarser series also contain the value. The E3 values are 1.0, 2.2 and 4.7, and E6 adds 1.5, 3.3 and 6.8.

E48 and E96 values

One decade of E96, the series used for ±1 % resistors; multiply by a power of ten for real values (1.00 → 100 Ω, 1 kΩ, 10 kΩ). Bold values are also E48 values, every second one. E96 is not a superset of E24: of the 24 E24 values only 1.0, 1.1, 1.3, 1.5, 2.0, 7.5 appear in it, which is why a 1 % catalogue often lists E24 values alongside the E96 ones, and why 1 % SMD parts in values such as 4.7 kΩ carry a 3-digit code rather than an EIA-96 code.

E192 values

E192 doubles E96 again for tolerances of ±0.5 % and tighter. Every second value is an E96 value (in bold). The highlighted 9.20 is the one place where the printed list departs from the formula. Even E192 misses 13 of the E24 values, among them 2.2, 2.7, 3.0, 3.3.

How to pick the nearest standard value

A calculation rarely lands on a standard value. Because the series are spaced by ratio, “nearest” means nearest on a log scale: find the series values either side, and the target is closer to the lower one if it is below their geometric mean, the square root of their product. For 4.6 kΩ in E12 the neighbours are 3.9 kΩ and 4.7 kΩ, and the nearest is 4.7 kΩ. For 9.5 kΩ in E24 the neighbours are 9.1 kΩ and 10 kΩ; their geometric mean is 9.539 kΩ, so 9.5 kΩ rounds down to 9.1 kΩ even though it looks closer to 10 kΩ.

Nearest is not always best. Round towards the safe side of the circuit: an LED’s series resistor goes up to the next value so the current stays at or below the target, which is what the LED resistor calculator does. In a divider the output is not linear in either resistor, so the voltage divider calculator tries the values on both sides and keeps the one that puts the output closest to the target. And a pair of values often beats one: two E24 resistors in series or parallel reach almost any ratio within a fraction of a percent.

Look up a value and its code

Type any resistance into the SMD resistor code calculator with Find the marking selected: it shows whether the value is in E24 or E96, the nearest values in both series, and the codes a chip resistor would carry. For through-hole parts, the resistor colour code calculator checks the bands against the series that matches their tolerance.

Capacitors and inductors

IEC 60063 covers capacitors too, but they are made in fewer values than resistors. Ceramic capacitors follow E24 or E12: KEMET’s C0G ranges include E24 decade values and its X7R ranges are E24 in some sizes and E12 in others. Aluminium electrolytics come in far fewer: one mainstream radial series (Nichicon UVR) offers 1, 2.2, 3.3, 4.7, 10, 22, 33, 47 µF and so on, mostly 1.0, 2.2, 3.3 and 4.7 per decade, a subset of E6. SMD power inductors from Bourns are listed in E12 values, with extra in-between values below 10 µH to hit current ratings. Those last two observations rest on one series or one maker each, so check the catalogue of the parts you buy.

Reading the value printed on a capacitor is a separate job: the three-digit picofarad code is decoded by the capacitor code calculator.

How we checked: every list on this page is generated from our research data, where the E3 to E192 lists were extracted from two independent Vishay value tables that agree cell for cell. The exceptions and the nesting were recomputed when this page was built.