Resistor Series & Tolerances

A practical overview of preferred values (E-series) and typical tolerances, from E6 to E192. Use this to pick realistic component values and understand accuracy limits.

What are E-Series?

The E-series are standardized preferred values spaced geometrically within each decade so that available parts cover the range with a given tolerance. The EN series has N values per decade. Nominals are approximately:

R_i ≈ 10^i/N for i = 0 … N-1 (rounded to a sensible number of digits).

Series	Values/Decade	Typical Tolerance	Common Use
E6	6	±20%	Very coarse; legacy/carbon comps, rough dividers
E12	12	±10%	General purpose; older stock, low-cost
E24	24	±5%	Through-hole carbon film, common SMD
E48	48	±2%	Better precision film
E96	96	±1%	Precision SMD/metal film (very common)
E192	192	±0.5%, ±0.25%, ±0.1%	High precision networks & instrumentation

Tolerance classes vary by manufacturer and series; the pairings above are the typical industry mappings.

One-Decade Examples (Nominals)

Values below show the base decade (1.00 to <10). Multiply/divide by powers of ten for other decades (e.g., x10 → 10 Ω series, x1k → kΩ series).

Series	Representative Values (one decade)
E6	1.01.52.2 3.34.76.8
E12	1.01.21.51.8 2.22.73.33.9 4.75.66.88.2
E24	1.01.11.21.3 1.51.61.82.0 2.22.42.73.0 3.33.63.94.3 4.75.15.66.2 6.87.58.29.1
E48	48 values per decade; examples: 1.00, 1.05, 1.10, 1.15, 1.21, 1.27, 1.33, 1.40, …
E96	96 per decade; examples: 1.00, 1.02, 1.05, 1.07, 1.10, 1.13, 1.15, 1.18, 1.21, 1.24, …
E192	192 per decade; examples: 1.00, 1.01, 1.02, 1.03, 1.04, … (very fine spacing)

Rounding: Manufacturers round to 2-3 significant digits (E24 often 2, E96/E192 usually 3). Actual offered values can vary slightly by vendor.

Worked Examples

Target 7.5 kΩ, ±5% design.
E24 (±5%) includes 7.5 in the decade set → choose 7.5 kΩ, 5%.
Target 3.3 kΩ, ±1% precision.
E96 (±1%) includes 3.32 and 3.24. For 3.3 kΩ nominal, 3.32 kΩ (1%) is a standard choice; error vs 3.30 kΩ is +0.6% (within ±1%).
Target 2.00 kΩ exact divider leg, ±0.1% budget.
Use E192 (±0.1%). E192 contains 2.00 in the decade set → 2.00 kΩ, 0.1% is available in precision series.
Back-checking tolerance window.
For 10 kΩ, 5%: range is 9.5-10.5 kΩ.
For 10 kΩ, 1%: range is 9.9-10.1 kΩ.
Choosing series by spec need.
If the design requires ±2% accuracy after trimming, start with E48 (±2%) or E96 (±1%) to ensure nominal availability and tighter drift options.

Markings (quick note)

Through-hole: color bands (4-band typically 5% E24; 5-band for 1% E96).
SMD 5%: 3-digit codes (e.g., 103 = 10 kΩ).
SMD 1% (E96): EIA-96 codes (two-digit + letter multiplier).

Tolerance vs. Series - Practical Guide

Need	Pick	Why
Rough biasing, LED resistors where ±10-20% is fine	E12 (±10%) or E24 (±5%)	Low cost, widely stocked, adequate spread
Filters, gain-set parts, ADC refs (general precision)	E96 (±1%)	Good accuracy and availability in SMD
Instrumentation, metrology, calibrations	E192 (≤±0.1%)	Very fine granularity and tight tolerance options

Remember: tolerance is about how far the actual value can be from nominal at room conditions. Temperature coefficient (e.g., 50-200 ppm/°C) and drift with time also matter for precision designs.

Simple Cheat Sheet

Series	Per Decade	Typical Tolerance	Example Base Values (1-10)
E6	6	±20%	1.0, 1.5, 2.2, 3.3, 4.7, 6.8
E12	12	±10%	1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2
E24	24	±5%	1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1
E48	48	±2%	1.00, 1.05, 1.10, 1.15, 1.21, 1.27, 1.33, 1.40, …
E96	96	±1%	1.00, 1.02, 1.05, 1.07, 1.10, 1.13, 1.15, 1.18, 1.21, 1.24, …
E192	192	≤±0.1%	1.00, 1.01, 1.02, 1.03, 1.04, …

How to choose Pick the required tolerance → match the E-series → select the nearest nominal. Verify the tolerance window covers your required min/max. For tighter error, step up the series or tolerance class.