E-Series Preferred Values: E6, E12, E24 & E96

1. Introduction

Walk into any electronics supplier and you'll never find a "1.37 kΩ" resistor on the shelf. You'll find 1.3 kΩ, 1.5 kΩ, 1.6 kΩ — values that follow a repeating pattern. That pattern is the E‑series, the family of preferred values that standard parts are made in.

Preferred values are a standardized, repeating set of numbers (within each factor‑of‑ten "decade") that manufacturers agree to produce. Instead of making a part for every possible value, the industry makes a fixed grid of values per decade, and the grid repeats for every power of ten: the same 12 numbers appear as 1.0–8.2, then 10–82, then 100–820, and so on.

This standardization exists for very practical reasons:

• Manufacturing & stocking. A finite set of values per decade means a supplier can stock a manageable range that still covers nearly every real‑world need.
• Cost. High volume per value keeps prices low; exotic one‑off values would be expensive to make and buy.
• Selection simplicity. Engineers pick the nearest standard value to a calculated target instead of specifying arbitrary numbers.
• Compatibility. A shared grid means a 4.7 kΩ from one maker is interchangeable with a 4.7 kΩ from another.

The grids are closely tied to tolerance. A component is never exactly its marked value — a "10 kΩ" part might really be 9.8 to 10.2 kΩ. The E‑series spacing was chosen so that, for a typical tolerance, the tolerance bands of neighbouring values roughly meet, leaving little or no gap in the range you can effectively reach. We'll look at that relationship carefully (and precisely) in the sections below.

2. E-Series overview

The "E" stands for a set of standard preferred-number series. The number after "E" is the count of nominal values in one decade (a factor‑of‑ten range, e.g. 1.0 to 10.0). So E12 has 12 values per decade, E24 has 24, and so on. The four series you'll meet most often are E6, E12, E24 and E96.

3. The mathematical foundation

Preferred values are spread geometrically (multiplicatively) across each decade, not arithmetically. Equal ratios between neighbours give even logarithmic spacing — which is exactly what you want when a "step up" should mean the same percentage change whether you're at a few ohms or a few megaohms.

The idealized generator for an EN series is:

• N is the number of preferred values per decade.
• n is the position within the decade (0 to N−1).
• When n = 0, V = 10⁰ = 1.0; when n = N, V = 10¹ = 10.0 (the start of the next decade).

The published standard values are the rounded, standardized versions of these idealized points — adjusted to convenient numbers and tuned so that tolerance bands of adjacent values roughly meet. You can see the difference in the E12 example below: the ideal 10^(n/12) points versus the actual E12 values.

Notice the small adjustments (2.610 → 2.7, 3.162 → 3.3, 4.642 → 4.7): the standard values are deliberately nudged so they're convenient and so the spacing still covers the range with a typical tolerance. The same 12 numbers then repeat in the next decade simply by multiplying by 10: 1.0–8.2 → 10–82 → 100–820 → 1 k–8.2 k, forever.

4. E6 — six values per decade

E6 is the coarsest commonly used series. Its wide spacing makes sense for components with wide tolerances (classically ±20%): because the ratio between adjacent E6 values (~1.5) roughly matches the ratio a ±20% tolerance band spans, neighbouring parts' tolerance ranges nearly meet, so there's no "hole" you can't fill.

Each row of the table is the same six numbers scaled by a power of ten. So "4.7" means 4.7 Ω, 47 Ω, 470 Ω, 4.7 kΩ, 47 kΩ… depending on the decade. E6 is common for basic resistors, some capacitors, and anything where ±5–20% is plenty.

5. E12 — twelve values per decade

E12 doubles the resolution of E6 and is the workhorse for general‑purpose resistors (traditionally ±5%). Every E6 value is also an E12 value — the coarser series is a subset of the finer one, which the highlight below shows.

E12 gives you a standard value within about ±5% of almost any target, which is why it dominates through‑hole resistor stock. If your calculated value isn't exactly on the E12 grid, you pick the nearest one and accept (or compensate for) the difference.

6. E24 — twenty-four values per decade

E24 is twice as fine as E12 and is the natural choice when you need a closer match, typically with ±2% (and ±1%/±5%) parts. It contains every E12 value (and therefore every E6 value).

E24 is where "common resistor value" selection usually lives for anything precision‑adjacent: bias networks, dividers and timing resistors where a few percent off would otherwise matter.

7. E96 — ninety-six values per decade

E96 is the fine grid behind modern ±1% (and tighter) SMD and thin‑film parts. It's so fine that it's usually selected by a 3‑digit code rather than by name: the first two digits are the E96 index (01–96) and the third is the power‑of‑ten multiplier (the "SMD code"). For example, code 473 = index 47 → 3.01, ×10³ = 3.01 kΩ.

One important subtlety: E96 is a finer, independently rounded grid. It is not a strict superset of E24 — some E24 values are approximated by the nearest E96 value (e.g. E24's 4.7 becomes E96's 4.75 or 4.64; E24's 9.1 becomes 9.09). The nesting E6 ⊂ E12 ⊂ E24 holds exactly, but E96 approximates rather than contains the coarser values.

8. Comparing E6, E12, E24 and E96

The figure below places each series on a single logarithmic decade. Bigger dots are coarser series, smaller dots finer ones. Because each coarser series is a subset of the next (E6 ⊂ E12 ⊂ E24), the large dots sit directly on top of the smaller ones — you can literally see that E96 is the same idea pushed to much finer resolution.

What changes as the series gets finer

• Coarse → fine spacing: higher N means more, closer values, so the nearest standard value is closer to your target.
• Relationship to tolerance: finer grids pair with tighter tolerances in practice, but tolerance is a separate spec — a ±5% part on a fine grid is still only good to ±5%.
• Availability: E6/E12/E24 are widely stocked through‑hole; E96 dominates SMD and thin‑film. Actual availability varies by type, package, power/voltage rating, dielectric, TCR and market.
• Resistor vs capacitor: resistors are commonly E12/E24/E96; capacitors are often coarser (E6/E12) for ceramic/film, with E12/E24 for tighter types — always check the specific family.
• Trade‑off: a finer series gets you closer, but if your circuit already has ±20% margin, a fine grid buys you nothing. Match the series to the tolerance the design actually needs.
• Prefer the neighbour: it's almost always better to pick the nearest standard value (or adjust the circuit) than to order a custom value, which is costlier, slower and harder to source later.

9. Practical selection examples

9.1 Choosing the nearest standard value

You calculate that a node needs 1630 Ω. How close can each series get?

The finer the series, the tighter the match. If 1.8% is fine for the circuit, an E24 1.6 kΩ is the economical choice; if you need it dead‑on, E96 1.62 kΩ is the way.

9.2 LED current‑limiting resistor

Drive a LED from 5 V; the LED drops 2.0 V and you want 10 mA. Required:

• E24 has 3.0 → 300 Ω exactly. I = 3 V / 300 Ω = 10.0 mA. ✓
• E6's nearest is 3.3 (330 Ω): I = 3 / 330 = 9.1 mA — still a perfectly good LED current.

Both work; the choice depends on the tolerance/series you have in stock.

9.3 Voltage divider

Make 3.3 V from a 5 V supply with a divider that draws only ~1 mA total. Pick R1 + R2 ≈ 10 kΩ, so ideal R2 = 6.6 kΩ and R1 = 3.4 kΩ. Choose standard values R1 = 3.3 kΩ, R2 = 6.8 kΩ (both E12):

That's +2.0% vs the 3.3 V target — acceptable for most logic supplies. The method is: set total resistance for current, compute the ideal ratio, pick the nearest standard values, then re‑compute the actual output and check the error.

9.4 When you actually need E96

Suppose the design calls for 4.99 kΩ. E12 offers only 4.7 kΩ (−5.4%) or 5.1 kΩ (+2.2%). E24 is no better (4.7 kΩ or 5.1 kΩ). But E96 has 4.99 kΩ exactly (SMD index 68). When your target lands between E12/E24 values and the error would be a problem, E96 is the only standard grid that reaches it.

9.5 Tolerance can negate a finer grid

You need a 10 kΩ ±1% reference. A 10 kΩ part is on E6/E12/E24/E96, so the nominal value is easy to find on any grid. But if you buy a ±5% 10 kΩ part (common on E24), its real value is anywhere in 9.5–10.5 kΩ — the ±5% tolerance dominates and a finer nominal grid helps you nothing. To hold ±1% you must buy a ±1% (E96) part. The grid and the tolerance are two separate things you both have to match to the design.

9.6 Scaling a value across decades

The same 12 E12 numbers repeat every factor of ten. The E12 value 4.7 therefore appears as 47 Ω (×10), 470 Ω (×100), 4.7 kΩ (×10³), 47 kΩ (×10⁴) and 470 kΩ (×10⁵) — identical ratio structure, just shifted. Master one decade and you know them all.

10. Key terms, precisely

• Nominal value — the value a part is labelled with (e.g. "10 kΩ").
• Preferred value — a value on the standard E‑series grid that parts are actually manufactured in.
• Standard value series — the grid itself (E6/E12/E24/E96), a repeating set of ratios per decade.
• Tolerance — the allowed manufacturing deviation around nominal, e.g. ±5%. A separate spec from the series.
• Actual (measured) value — the resistance a given physical part truly has, within its tolerance.
• Accuracy — how close the actual value is to a specified target; bounded by tolerance plus any selection error.
• Manufacturer availability — which values actually exist, which varies by component type, package, power/voltage rating, dielectric, TCR and market. "Standard" ≠ "in stock right now."

11. Nearest preferred‑value finder

Enter a target value and a series; the tool finds the closest standard value, its exact value, the deviation, and — for E96 — the SMD index. It searches across decade boundaries, so values near a power of ten resolve correctly.

12. Quick reference

13. Technical references

• IEC 60063 — Preferred number series RC, RD, C and CD for electronic components. Defines the E6/E12/E24/E96 preferred‑number series used throughout this guide.
• EIA‑96 / SMD 3‑digit resistor codes — the code convention where the first two digits index the E96 value and the third is the ×10 multiplier.
• Component manufacturer datasheets and marking guides, for part‑family‑specific availability and tolerances.