Resistors

Color band systemedit

To distinguish left from right there is a gap between the C and D bands:

In the above example, a resistor with bands of red, violet, green, and gold has first digit 2 (red; see table below), second digit 7 (violet), followed by 5 (green) zeroes: 2700000 ohms. Gold signifies that the tolerance is ±5%.

Precision resistors may be marked with a five band system, to include three significant digits, a power of 10 multiplier, and a tolerance band. An extra-wide first band indicates a wire-wound resistor.

Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details.

Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient, in units of ppm/K.

All coded components have at least two value bands and a multiplier; other bands are optional.

The standard color code per IEC 60062:2016 is as follows:

Ring color			Significant figures	Multiplier		Tolerance		Temperature coefficient
Name	Code	RAL				Percent %	Letter	ppm/K	Letter
None	–	–	–	–		±20	M	–
Pink	PK	3015	–	×10−3	×0.001	–		–
Silver	SR	–	–	×10−2	×0.01	±10	K	–
Gold	GD	–	–	×10−1	×0.1	±5	J	–
Black	BK	9005	0	×100	×1	–		250	U
Brown	BN	8003	1	×101	×10	±1	F	100	S
Red	RD	3000	2	×102	×100	±2	G	50	R
Orange	OG	2003	3	×103	×1000	±0.05	W	15	P
Yellow	YE	1021	4	×104	×10000	±0.02nb	P	25	Q
Green	GN	6018	5	×105	×100000	±0.5	D	20	Znb
Blue	BU	5015	6	×106	×1000000	±0.25	C	10	Znb
Violet	VT	4005	7	×107	×10000000	±0.1	B	5	M
Grey	GY	7000	8	×108	×100000000	±0.01nb nb	L (A)	1	K
White	WH	1013	9	×109	×1000000000	–		–

Resistors use various E series of preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude: ... 0.68, 6.8, 68, 680, ... For resistors of 20% tolerance the E6 series, with six values: 10, 15, 22, 33, 47, 68, then 100, 150, ... is used; each value is approximately the previous value multiplied by 6√10. For 10% tolerance resistors the E12 series, with 12√10 as multiplier, is used; similar schemes up to E192, for 0.5% or tighter tolerance are used. The separation between the values is related to the tolerance so that adjacent values at the extremes of tolerance approximately just overlap; for example, in the E6 series 10 + 20% is 12, while 15 − 20% is also 12.

Zero ohm resistors, marked with a single black band, are lengths of wire wrapped in a resistor-like body which can be mounted on a printed-circuit board (PCB) by automatic component-insertion equipment. They are typically used on PCBs as insulating "bridges" where two traces would otherwise cross, or as soldered-in jumper wires for setting configurations.

Body-end-dot systemedit

The "body-end-dot" or "body-tip-spot" system was used for cylindrical composition resistors sometimes still found in very old equipment (built before the Second World War); the first band was given by the body color, the second band by the color of one end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was in the body color, silver, or gold for 20%, 10%, 5% tolerance (tighter tolerances were not routinely used).

Examplesedit

From top to bottom:

• Green, blue, black, black, brown
  • 560 ohms ±1%
• Red, red, orange, gold
  • 22000 ohms ±5%
• Yellow, violet, brown, gold
  • 470 ohms ±5%
• Blue, grey, black, gold
  • 68 ohms ±5%

The physical size of a resistor is indicative of the power it can dissipate.

There is an important difference between the use of three and of four bands to indicate resistance. The same resistance is encoded by:

• Red, red, orange = 22 followed by 3 zeroes = 22000 (excluding default, silver, or gold tolerance)
• Red, red, black, red = 220 followed by 2 zeroes = 22000 (excluding brown or other band for tolerance)

Mnemonicsedit

Useful mnemonics have been created to make it easier to remember the numeric order of resistor color bands. The following example includes the tolerance codes gold, silver, and none:

• Bad Beer Rots Out Your Guts But Vodka Goes Well – Get Some Now.

The colors are sorted with ascending values in the order of the visible light spectrum to make them easy to remember and to reduce the significance of possible read errors due to color shifts and fading over time: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.