Resistors

Resistors are passive electronic components.

Examples of 5% tolerance 1/4 W resistors. Note the "bumps."

Identification

Resistors' values are shown on the resistor, coded in a series of colored bands.

The resistors in labs here in Pratt are almost all 5% resistors or 1% resistors. That is, their actual values are either are guaranteed to be within 5% or 1% of the nominal, or labeled value.

The 5% resistors have three bands showing their value: two significant figures, and then the number of zeros.

The 1% resistors have four bands showing their value: three significant figures, and then the number of zeros.

For most of the resistors found around here, the last band will indicate the tolerance. For 5% resistors, the tolerance band will be the fourth band and will be the color gold. For 1% resistors the tolerance band will be the 5th band and will be brown.

In which order do you read the bands--left to right or right to left? Good question! You must use your intuition here. On 5% resistors, this is easy: the first significant figure will never be gold. If you read a 1% resistor and come up with an unlikely number, then you're probably reading it backward. Also, the first band is closer to the edge than the last band; on resistors with bulges at the ends, the first band is the one on the bulge.

"three band" (usually 5%) resistor color code:

Color	1st band	2nd band	3rd band (multiplier)	4th band (tolerance)
Black	0	0	×100
Brown	1	1	×101	±1% (F)
Red	2	2	×102	±2% (G)
Orange	3	3	×103
Yellow	4	4	×104
Green	5	5	×105	±0.5% (D)
Blue	6	6	×106	±0.25% (C)
Violet	7	7	×107	±0.1% (B)
Gray	8	8	×108	±0.05% (A)
White	9	9	×109
Gold			×10-1	±5% (J)
Silver			×10-2	±10% (K)
None				±20% (M)

"four band" (usually 1%) resistor color code:

Color	1st band	2nd band	3rd band	4th band (multiplier)	5th band (tolerance)
Black	0	0	0	×100
Brown	1	1	1	×101	±1% (F)
Red	2	2	2	×102	±2% (G)
Orange	3	3	3	×103
Yellow	4	4	4	×104
Green	5	5	5	×105	±0.5% (D)
Blue	6	6	6	×106	±0.25% (C)
Violet	7	7	7	×107	±0.1% (B)
Gray	8	8	8	×108	±0.05% (A)
White	9	9	9	×109
Gold				×10-1	±5% (J)
Silver				×10-2	±10% (K)
None					±20% (M)

5% Resistor Standard Values

10	11	12	13	15	16	18	20	22	24	27	30
33	36	39	43	47	51	56	62	68	75	82	91

1% Resistor Standard Values

100	102	105	107	110	113	115	118
121	124	127	130	133	137	140	143
147	150	154	158	162	165	169	174
178	182	187	191	196	200	205	210
215	221	226	232	237	243	249	255
261	267	274	280	287	294	301	309
316	324	332	340	348	357	365	374
383	392	402	412	422	432	442	453
464	475	487	499	511	523	536	549
562	576	590	604	619	634	649	665
681	698	715	732	750	768	787	806
825	845	866	887	909	931	953	976

Examples

Four-band Resistor

A resistor that has bands (starting from the band on the part of the resistor with the largest radius) of blue-gray-brown-gold will be:

\( \mbox{blue }\mbox{ gray }*\mbox{ brown }\pm\mbox{ gold} \)

resistor, or 68 * 10 = 680±5% Ω.

Five-band resistor

A yellow-violet-red-white-silver resistor would be:

\( \mbox{yellow }\mbox{ violet }\mbox{ red }*\mbox{ white } \pm \mbox{ silver } \)

or 472 * 1000000000 = 472±10\% GΩ.

Note that the same value resistor will have a different multiplier band color in the four-band scheme than in the five-band scheme. A 1 kΩ resistor will be brown-black-red-TOL in the first case and brown-black-black-brown-TOL in the second.

Questions

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External Links

• Wikipedia page on Electronic color code
• Graphical resistance calculator by Danny Goodman