E-Series Standard Resistor Values: Complete Guide to E12, E24, E48, E96

Understand the preferred number system behind standard resistor values — why 4.7 kΩ exists but 4.5 kΩ doesn't, and how to choose the right E-series for your circuit.

Why Do Resistor Values Look "Weird"?

If you have ever browsed a resistor catalog, you have probably noticed something strange: values like 4.7 Ω, 3.3 kΩ, and 56 kΩ are everywhere, but you will never find a 4.5 kΩ or 3.0 kΩ resistor in the same series. This is not arbitrary — it is the result of a carefully designed system called preferred numbers, standardized under IEC 60063.

The idea is simple: given a tolerance band (say ±5%), the available values should overlap just enough that any real-world resistance can be approximated by at least one standard value within the tolerance. This minimizes the number of unique values manufacturers need to produce while ensuring designers can always find a part close to what they need.

The Math Behind Preferred Numbers

Each value in an E-series is derived from the formula:

where E is the series number (12, 24, 48, etc.) and n ranges from 0 to E−1. The result is then rounded to two or three significant figures. For example, in the E12 series:

• n=0: 10^(0/12) = 1.000 → 1.0
• n=1: 10^(1/12) = 1.212 → 1.2
• n=2: 10^(2/12) = 1.468 → 1.5
• n=3: 10^(3/12) = 1.782 → 1.8
• n=4: 10^(4/12) = 2.154 → 2.2
• n=5: 10^(5/12) = 2.610 → 2.7
• n=6: 10^(6/12) = 3.162 → 3.3
• n=7: 10^(7/12) = 3.831 → 3.9
• n=8: 10^(8/12) = 4.642 → 4.7
• n=9: 10^(9/12) = 5.623 → 5.6
• n=10: 10^(10/12) = 6.813 → 6.8
• n=11: 10^(11/12) = 8.254 → 8.2

These 12 base values then repeat for each decade: 10–82, then 100–820, then 1k–8.2k, and so on. The tolerance of ±10% for E12 means adjacent values just barely overlap — a 1.2 Ω resistor at +10% reaches 1.32 Ω, while a 1.0 Ω resistor at +10% reaches 1.1 Ω. There is a small gap (1.1 to 1.32 is covered), ensuring full coverage across the decade.

E-Series Comparison Table

Each E-series is matched to a tolerance class. More values per decade means tighter tolerance and more precise parts:

E12 Values (±10% Tolerance)

The E12 series is the most widely recognized set, commonly used with carbon film resistors:

Multiply by any power of 10 to get values in any decade. For example, the base value 4.7 gives you 4.7 Ω, 47 Ω, 470 Ω, 4.7 kΩ, 47 kΩ, 470 kΩ, and 4.7 MΩ.

E24 Values (±5% Tolerance)

E24 is the workhorse series for general-purpose metal film resistors. It includes all E12 values plus 12 additional values in between:

When you pick up a 4-band resistor with a gold tolerance band (±5%), its value comes from this series. Use our Resistor Color Code Calculator to decode any 4-band or 5-band resistor instantly.

E48 and E96 Values (±2% and ±1% Tolerance)

For precision designs, the E48 and E96 series provide much finer resolution. These values have three significant digits, which is why precision resistors use the 5-band color code system. The E96 series is particularly important for analog design:

Selected E96 values (the full series has 96 values per decade):

This same sequence repeats for each decade (10.0–97.6, 100–976, etc.). Note that each E96 value has three significant digits — for instance, 4.99 kΩ, not 5.0 kΩ. This precision is why E96 resistors use 5-band markings or EIA-96 SMD codes.

How to Choose the Right E-Series for Your Design

Selecting the correct E-series is a balancing act between precision, cost, and availability:

E24 (±5%) — The Default Choice

For most digital circuits, LED current-limiting resistors, pull-up/pull-down networks, and general-purpose applications, E24 is perfectly adequate. These resistors are the cheapest and most widely stocked. A 10 kΩ E24 resistor costs roughly $0.001 in bulk.

E96 (±1%) — Precision Analog Design

When you need accuracy — op-amp feedback networks, voltage divider references for ADCs, current-sensing resistors — step up to E96. The cost premium is small: a 1% metal film resistor typically costs 20–50% more than a 5% part, but the precision improvement is 5×. For a voltage divider setting a 2.5V reference from a 5V supply, using E96 values like 4.99 kΩ / 4.99 kΩ gives exactly 2.500V nominal, while the closest E24 pairing (4.7 kΩ / 4.7 kΩ) also works but with less margin for the exact midpoint.

E192 (±0.5% or Better) — Calibration and Measurement

Reserve E192 for instrumentation, calibration standards, and ultra-precision applications. These parts are expensive and often have long lead times. In 15+ years of engineering practice, most designers never need to go beyond E96.

Real-World Example: Designing a Voltage Divider

Suppose you need to monitor a 12V battery voltage with a 3.3V microcontroller ADC. You need a voltage divider that scales 12V down to 3.3V:

Now we need to find standard resistor values where R1 ≈ 2.636 × R2:

Using E24 values (±5%)

Try R2 = 10 kΩ → R1 = 26.36 kΩ. The closest E24 value is 27 kΩ. Let us check the actual output:

That is 1.7% below the target. For a battery monitor where you just need to know "is it above 11V?", this is fine. But if you need ±1% accuracy on the measurement, E24 is not cutting it.

Using E96 values (±1%)

Try R2 = 10.0 kΩ → R1 should be 26.36 kΩ. The closest E96 value is 26.1 kΩ:

That is only 0.7% above the target — much better. Even closer: R1 = 26.7 kΩ gives V_out = 3.176V (3.7% low), or you can try R2 = 10.2 kΩ, R1 = 26.7 kΩ:

Now we are within 0.7% of the ideal 3.3V. Use our Voltage Divider Calculator to quickly test different standard value combinations and find the best match.

Combining Resistors for Non-Standard Values

Sometimes no single E-series value gets you close enough. In those cases, you can combine two or more standard values:

Series Combination

Place two resistors in series to add their values. For example, if you need 25 kΩ but the closest E96 value is 24.9 kΩ (0.4% off), you can use 24 kΩ + 1.0 kΩ = 25.0 kΩ exactly. The downside is extra PCB area and cost.

Parallel Combination

Two equal resistors in parallel give half the value. For example, two 100 kΩ resistors in parallel = 50.0 kΩ. This is useful when 49.9 kΩ (E96) is not precise enough, or when you need a value that falls between E-series steps.

Use our Series/Parallel Resistor Calculator to experiment with different combinations and find the exact equivalent resistance you need.

Common Mistakes When Working with E-Series

• Assuming all values in a series are equally available: Just because a value exists in the E96 standard does not mean your distributor carries it. Always verify stock for precision values.
• Mixing E24 and E96 in the same circuit: If your design relies on a precise ratio (like a voltage divider), using one E24 and one E96 resistor defeats the purpose. Both resistors in a ratio-critical pair should come from the same series.
• Ignoring tolerance stack-up: Two ±1% resistors in a divider can produce up to ±2% error in the output voltage. Calculate the worst-case, not just the nominal.
• Forgetting temperature coefficients: A ±1% tolerance only applies at 25°C. For military or automotive temperature ranges, the actual value can drift far more. Check the datasheet's temperature coefficient (typically ±50 to ±100 ppm/°C for metal film).
• Using E12 for new designs: The cost savings of E12 over E24 are negligible today. Unless you are repairing vintage equipment, design with E24 as the minimum.

Quick Reference: E12 and E24 Full Tables

E12 Full Values (base decade)

E-Series and SMD Resistor Codes

The E-series directly determines which marking system an SMD resistor uses:

• E24 (±5%) → 3-digit SMD code: two significant digits plus multiplier. Example: "103" = 10 × 10³ = 10 kΩ.
• E96 (±1%) → 4-digit code or EIA-96 code: three significant digits plus multiplier. Example: "1002" = 100 × 10² = 10 kΩ. Or EIA-96: "01C" = 100 × 100 = 10 kΩ.

This connection between E-series and marking systems is why understanding preferred numbers helps you read SMD codes correctly. A 3-digit code always means E24, and a 4-digit or EIA-96 code means E96 or better.

Summary

The E-series preferred number system is the backbone of resistor (and capacitor) value standardization. Here is what to remember:

• E12/E24 for general-purpose work — cheap, available, good enough for digital circuits and LED driving.
• E96 for precision analog — voltage references, feedback networks, current sensing. The cost premium is small.
• E192 only for metrology and calibration — most engineers never need it.
• Always verify distributor stock for less common E96 values.
• For ratio-critical circuits, use resistors from the same series and calculate worst-case tolerance stack-up.

Ready to decode your resistors? Try our Resistor Color Code Calculator for through-hole parts, the LED Resistor Calculator for current-limiting design, or calculate custom resistance combinations with the Series/Parallel Resistor Calculator.