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Resistors and capacitors

Read resistor color bands and capacitor codes, find the nearest standard value or a pair of resistors that hits your target, and size LED resistors and voltage dividers.

Color code

4.7k, 4k7, 470R and 4R7 all work. Capital M is megohms.

4.7 kΩ ±5 %: anywhere from 4.465 kΩ to 4.935 kΩ. It is a standard E12, E24 value.

Standard values and combinations

Series
50E12475610121518222733396882E24511011131518202227303339435662687591E9649.9
One decade on a log scale. Each band is a value’s tolerance window: ±10 % for E12, ±5 % for E24 and ±1 % for E96. The windows sit side by side, so most values in the decade fall inside a window. Multiply by a power of ten for other decades.
Nearest E12 value
4.7 kΩ (-6 %)
Two in series
4.7 kΩ + 270 Ω = 4.97 kΩ (-0.6 %)
Two in parallel
10 kΩ in parallel with 10 kΩ = 5 kΩ (exact)

Marking codes

4.7 kΩ. This style marks ±2, ±5 or ±10 % (E24) parts.

100,000 pF = 100 nF, ±10 %.

Code 104

LED series resistor

V
LED
V
V
mA

Kingbright WP7113ID datasheet, at its test current. Its absolute maximum is 30 mA.

5 V330 Ωdrops 3.1 V1.9 V9.39 mA

The resistor must drop 3.1 V at 10 mA, which takes 310 Ω. The next E24 value up is 330 Ω, giving 9.39 mA with a typical LED and 8.18 mA if its forward voltage is at the maximum. The resistor dissipates 29.1 mW.

Voltage divider

V
Ω
Ω
Ω

Leave empty for no load.

12 VR1 10 kΩR2 10 kΩ6 V out

Unloaded, the output is 6 V, the fraction R2 / (R1 + R2) of the input. The divider draws 600 µA and R1 dissipates 3.6 mW.

Try this

  1. Yellow and violet are the digits 4 and 7, and the red third band multiplies by 100: 47 × 100 = 4 700 Ω. Gold means ±5 %.

  2. There is no 5 kΩ in E12. Its neighbors are 4.7 kΩ and 5.6 kΩ, and their ±10 % windows meet, so no value is far from a standard part. Two 10 kΩ resistors in parallel make exactly 5 kΩ.

  3. This datasheet gives the blue LED a typical forward voltage of 3.3 V, so a 3.3 V supply leaves nothing for the resistor. Try 5 V.

  4. Two 10 kΩ resistors split 12 V into 6 V, but a 10 kΩ load in parallel with R2 pulls the output down to 4 V. Keep the load much larger than R2.

Apply it

  • Measure parts before you solder them. An ohmmeter applies a small current and measures the resulting voltage, so measure with the circuit unpowered (Technician pool T7D05 and T7D11).
  • Avoid wire-wound resistors in RF circuits: their inductance can make the circuit behave unpredictably (General pool G6A06).
  • Check the power rating as well as the value. Vishay rates its 0207-size metal film resistor at 0.6 W with the surroundings at 70 °C or cooler, and the allowed power falls above that (Vishay document 28766).
  • Read the bands starting from the end they are grouped toward. Four-band codes mark ±5 % parts and five-band codes mark ±1 % and tighter (Vishay document 20020).

How it works

  • Standard values come from the E series: E12 for ±10 % parts, E24 for ±5 % and ±2 %, and E96 for ±1 %. Successive values step by about the 12th, 24th or 96th root of 10, and every decade repeats the same numbers.
  • The color code follows IEC 60062. On a four-band resistor the first two bands are digits, the third is the multiplier and the fourth the tolerance; a five-band resistor has three digit bands.
  • Chip resistors are marked with three characters for ±2, ±5 and ±10 % parts (472 is 4.7 kΩ) and four for ±1 % and tighter (4701 is 4.7 kΩ). R marks a decimal point in ohms and L one in milliohms.
  • Capacitor codes give picofarads as two significant digits and a multiplier: 104 is 100 000 pF, or 0.1 µF. A third digit of 9 or 8 divides by 10 or 100 for values under 10 pF. A trailing letter is the tolerance, such as K for ±10 %.
  • An LED series resistor drops the difference between the supply and the LED forward voltage at the chosen current. Forward voltages for the presets are from Kingbright 5 mm LED datasheets.
  • Series resistances add, and two resistors in parallel combine as their product over their sum. A divider passes R2 / (R1 + R2) of its input, and a load in parallel with R2 lowers the output.

Learn more: Building your own gear

Sources: Standard Electronic Decade Value Tables (document 31001) (Vishay Dale); Surface Mount Resistor Marking, with the IEC 60062 color code (document 20020) (Vishay Draloric); Surface Mount Multilayer Ceramic Chip Capacitors, C0G (C1003) (KEMET); S Series Ceramic Disc Capacitors (document 28515) (Vishay); MBA/SMA 0204, MBB/SMA 0207, MBE/SMA 0414 Professional Metal Film Leaded Resistors (document 28766) (Vishay Beyschlag); WP7113ID 5 mm red LED datasheet (Kingbright); WP7113YD 5 mm yellow LED datasheet (Kingbright); WP7113GD 5 mm green LED datasheet (Kingbright); WP7113QBC/D 5 mm blue LED datasheet (Kingbright); College Physics 2e, 21.1 Resistors in Series and Parallel (OpenStax (Rice University)); Radio Mathematics (ARRL Handbook supplement) (ARRL); 2026-2030 Technician question pool (NCVEC Question Pool Committee); 2023-2027 General question pool (NCVEC Question Pool Committee)

Practice the exam questions: T6 Electronic and Electrical Components (Technician), G6 Circuit Components (General)

Found something wrong or out of date? Report a problem with this tool on GitHub (a public issue; nothing is sent until you submit it there).