IEC 60063 · E12 · E24 · E48 · E96 · E192

Standard resistor value calculator

Find the closest standard value for any resistance, design voltage dividers and attenuators, work out RC charge and discharge timing, or size a supercapacitor bank. Single parts, series or parallel pairs, with colour codes. Everything is computed in your browser.

Target value

Resistance (Ω)

Accepted: 4700 · 4.7k · 4k7 · 0R47 · 2.2M · 150m (milliohms)

Examples

Comparison by series

Closest single value and best two-resistor pairs in each series, with the relative error to your target.

Series	Single	Error	Series R1 + R2	Error	Parallel R1 ∥ R2	Error

Highlighted cells: overall best match. Disabled combinations show “—”. Error sign: negative = below target.

Divider specification

Vin (V)

Ratio Vout / Vin

Divider current (mA)

Ratio examples (fractions accepted)

Allowed current deviation

Comparison by series

Best divider found in each series, within the allowed current deviation.

Series	R1 (top)	R2 (bottom)	Ratio	Error	Current	Parts

Highlighted row: overall best divider. Ratio = R2 / (R1 + R2).

Attenuator specification

Vin is applied across Ra + Rm + Rb, Vout is taken across the middle resistor Rm. Ra = Rb keeps both legs symmetric.

Vin (V)

Ratio Vout / Vin

Branch current (mA)

Ratio examples (fractions accepted)

Allowed current deviation

Comparison by series

Best attenuator found in each series, within the allowed current deviation.

Series	Ra = Rb (outer)	Rm (output)	Ratio	Error	Current	Parts

Highlighted row: overall best. Ratio = Rm / (Ra + Rm + Rb); “Parts” counts both Ra and Rb.

RC circuit

Mode

Supply voltage Vs (V)

Initial voltage V0 (V)

Resistance R (Ω)

Capacitance C (F)

Accepted: 100n · 4u7 · 2.2µF · 470p · 1m (mF)

Time t

Target voltage (V)

Desired delay to reach the target (find C)

Times: 250ns · 47us · 1.5ms · 2s · 3min (no unit = seconds)

RC charge · time constant

Vc(t) time t target voltage final voltage

Drag to move t

Time-constant table

Capacitor voltage and current at common multiples of τ = RC.

Time constants	Time	Vc	Step completed	Current

Standard capacitor for the desired delay

Supercapacitor bank

Required energy (J)

Bus voltage (V, optional)

Cell capacitance (F)

Cell max voltage (V)

Cell ESR (Ω, optional)

Cell leakage (A, optional)

Examples: energy 500 or 2k (kJ) · capacitance 100 or 3000 (F) · ESR 15m = 15 mΩ · leakage 10u = 10 µA. Leave the bus voltage empty to compare layouts at full cell voltage.

Charging from 0 V at constant current

Charge current (A)

Bank configurations

Layout	Cells	Bank C	Charge V	V per cell	Energy	Charge time	Bank ESR	Action

Highlighted row: configuration shown above. Energy per cell is the same in every layout, so the cell count only grows when rounding up the parallel count.

E-series standard value tables

Preferred values per decade defined by IEC 60063. Multiply by any power of ten: 4.7 gives 4.7 Ω, 47 Ω, 470 Ω, 4.7 kΩ, 47 kΩ…

E3 — 3 values per decade (over ±20 % (rarely used))

E6 — 6 values per decade (±20 % · common for capacitors)

E12 — 12 values per decade (±10 %)

E24 — 24 values per decade (±5 %)

E48 — 48 values per decade (±2 %)

1.00
1.05
1.10
1.15
1.21
1.27
1.33
1.40
1.47
1.54
1.62
1.69
1.78
1.87
1.96
2.05
2.15
2.26
2.37
2.49
2.61
2.74
2.87
3.01
3.16
3.32
3.48
3.65
3.83
4.02
4.22
4.42
4.64
4.87
5.11
5.36
5.62
5.90
6.19
6.49
6.81
7.15
7.50
7.87
8.25
8.66
9.09
9.53

E96 — 96 values per decade (±1 %)

1.00
1.02
1.05
1.07
1.10
1.13
1.15
1.18
1.21
1.24
1.27
1.30
1.33
1.37
1.40
1.43
1.47
1.50
1.54
1.58
1.62
1.65
1.69
1.74
1.78
1.82
1.87
1.91
1.96
2.00
2.05
2.10
2.15
2.21
2.26
2.32
2.37
2.43
2.49
2.55
2.61
2.67
2.74
2.80
2.87
2.94
3.01
3.09
3.16
3.24
3.32
3.40
3.48
3.57
3.65
3.74
3.83
3.92
4.02
4.12
4.22
4.32
4.42
4.53
4.64
4.75
4.87
4.99
5.11
5.23
5.36
5.49
5.62
5.76
5.90
6.04
6.19
6.34
6.49
6.65
6.81
6.98
7.15
7.32
7.50
7.68
7.87
8.06
8.25
8.45
8.66
8.87
9.09
9.31
9.53
9.76

E192 — 192 values per decade (±0.5 %, ±0.25 %, ±0.1 % and better)

1.00
1.01
1.02
1.04
1.05
1.06
1.07
1.09
1.10
1.11
1.13
1.14
1.15
1.17
1.18
1.20
1.21
1.23
1.24
1.26
1.27
1.29
1.30
1.32
1.33
1.35
1.37
1.38
1.40
1.42
1.43
1.45
1.47
1.49
1.50
1.52
1.54
1.56
1.58
1.60
1.62
1.64
1.65
1.67
1.69
1.72
1.74
1.76
1.78
1.80
1.82
1.84
1.87
1.89
1.91
1.93
1.96
1.98
2.00
2.03
2.05
2.08
2.10
2.13
2.15
2.18
2.21
2.23
2.26
2.29
2.32
2.34
2.37
2.40
2.43
2.46
2.49
2.52
2.55
2.58
2.61
2.64
2.67
2.71
2.74
2.77
2.80
2.84
2.87
2.91
2.94
2.98
3.01
3.05
3.09
3.12
3.16
3.20
3.24
3.28
3.32
3.36
3.40
3.44
3.48
3.52
3.57
3.61
3.65
3.70
3.74
3.79
3.83
3.88
3.92
3.97
4.02
4.07
4.12
4.17
4.22
4.27
4.32
4.37
4.42
4.48
4.53
4.59
4.64
4.70
4.75
4.81
4.87
4.93
4.99
5.05
5.11
5.17
5.23
5.30
5.36
5.42
5.49
5.56
5.62
5.69
5.76
5.83
5.90
5.97
6.04
6.12
6.19
6.26
6.34
6.42
6.49
6.57
6.65
6.73
6.81
6.90
6.98
7.06
7.15
7.23
7.32
7.41
7.50
7.59
7.68
7.77
7.87
7.96
8.06
8.16
8.25
8.35
8.45
8.56
8.66
8.76
8.87
8.98
9.09
9.20
9.31
9.42
9.53
9.65
9.76
9.88

Frequently asked questions

What are E-series resistor values?

The E-series defined by IEC 60063 are preferred numbers spaced geometrically within each decade. E12 has 12 values (±10 %), E24 has 24 (±5 %), E48 has 48 (±2 %), E96 has 96 (±1 %) and E192 has 192 (±0.5 % and better). E12 and E24 use two significant digits, the others three.

How do I get a value that is not in a series?

Combine two standard resistors. In series R = R1 + R2; in parallel R = R1·R2 / (R1 + R2). A pair from E12 or E24 often gets closer than a single precision part, and the combination keeps the tolerance of its parts.

How is a voltage divider calculated?

Vout = Vin · R2 / (R1 + R2). The divider current sets the overall scale, R1 + R2 = Vin / I. The worst case assumes R1 and R2 drift in opposite directions within their tolerance.

What is a differential attenuator?

Three resistors in series across Vin, with the output taken across the middle one: Vout = Vin · Rm / (Ra + Rm + Rb). Keeping Ra = Rb makes both legs symmetric, which helps common-mode rejection.

How fast does a capacitor charge through a resistor?

Vc(t) = Vf + (V0 − Vf) · e^(−t/RC). After one time constant τ = RC the capacitor has covered 63.2 % of the step, 95 % after 3τ and 99.3 % after 5τ. Capacitors usually come in E6 or E12 values.

How do I size a supercapacitor bank?

Ns groups in series of Np cells in parallel give C = Ccell·Np/Ns, a rated voltage of Ns·Vcell and E = ½·C·V². The bank ESR is ESRcell·Ns/Np. Cells in series must be balanced so none exceeds its rated voltage.

How do I read the resistor colour code?

E12 and E24 parts use 4 bands: two digits, a multiplier and the tolerance. From E48 upward, 5 bands are used: three digits, a multiplier and the tolerance (red ±2 %, brown ±1 %, green ±0.5 %).