Resistor color code calculator

How to read a resistor's colour code

1. Turn the resistor so the tolerance band is on the right: it is usually gold, silver or brown, and often sits a little apart from the others. The first band is the one nearest a lead.
2. Count the bands and pick 3, 4, 5 or 6 above.
3. Tap a band on the drawing (or its name under it), then tap its colour. The next band is selected for you.
4. Read the value, the tolerance and the range the real part may measure. On 6 bands the last band is the temperature coefficient in ppm/K.
5. To go the other way, open Value → bands, type 4k7, 4.7k, 4700, 4R7 or R47, and pick a series to see the nearest standard values. For chip resistors, open SMD code.

Worked example: why your 5 kΩ is not in the drawer

Resistors are made in the E series of IEC 60063, not in round numbers. Each series spaces its values evenly on a log scale so that neighbouring tolerance windows meet: E24 has 24 values per decade for ±5 % parts, E96 has 96 for ±1 %. A circuit that calls for 5,000 Ω gets one of the neighbours. In E24 those are 4.7 kΩ (6 % low) and 5.1 kΩ (2 % high); in E96 they are 4.99 kΩ (0.2 % low) and 5.11 kΩ (2.2 % high). The 4.99 kΩ part, yellow-white-white-brown-brown, is within its own 1 % of 5 kΩ. 4.7 kΩ is in E12 and E24 but not in E48 or E96, which use 4.64 and 4.75 instead; the calculator tells you which series a value belongs to.

The tolerance is a promise about a new part: 4.7 kΩ ±5 % may measure anywhere from 4,465 to 4,935 Ω and still be in spec. It says nothing about how far the part drifts later with heat and age.

SMD resistor codes

Chip resistors carry a number instead of bands. 3 digits: two digits and the number of zeros, so 472 = 47 × 10² = 4.7 kΩ and 100 = 10 Ω (not 100 Ω). 4 digits: three digits and the zeros, so 4702 = 47.0 kΩ and 1001 = 1.00 kΩ. R notation: R is the decimal point, so 4R7 = 4.7 Ω and R47 = 0.47 Ω. EIA-96 (now part of IEC 60062): two digits pick one of the 96 values of the E96 series and a letter is the multiplier, so 01C = 100 × 100 = 10.0 kΩ and 68X = 499 × 0.1 = 49.9 Ω. 0, 00 or 000 is a zero-ohm link. Many of the smallest chips carry no marking at all; then only the reel label says what they are.

What it cannot do

• It cannot read a photo of a resistor. You tap the colours yourself: faded bands, brown next to red and orange, and violet next to grey fool cameras and eyes alike, so in doubt, check the part with a meter.
• A resistor's real value can drift from its marking: heat, age and overload move it, and a burnt part can read anything. The bands tell you what it was meant to be; a meter, with the part out of the circuit, tells you what it is now.
• It cannot tell which end is which on a symmetric code. It warns when the bands only make sense read the other way round (for example when a gold band comes first), or when a reading starts with a rare black band, but some codes are valid both ways.
• It reads the IEC 60062:2016 meanings. Before 2016 some makers used yellow and grey tolerance bands for other values, and old parts may follow older codes; there the maker's datasheet wins.
• EIA-96 letters are those of the table it uses (Y/S, X/R, A, B/H, C, D and E). A letter outside it, such as Z or F on some datasheets, is reported as unknown rather than guessed. A code like 68R is read as 68 Ω in R notation, with the rarer EIA-96 reading (49.9 Ω) shown beside it.
• It is for resistors only: capacitor and inductor colour codes differ.

Privacy

Everything is worked out in this page; nothing is saved and nothing you type leaves your device. The page sends an anonymous page-view count and one of two fixed words, resistor-calc and resistor-smd, never a colour or a value.

Questions

How do you read a 5 band resistor?

Hold it with the tolerance band, usually brown for 1 %, on the right. Bands 1, 2 and 3 are digits, band 4 is the multiplier and band 5 the tolerance. Brown-black-black-red-brown is 1, 0, 0, times 100, so 10,000 Ω = 10 kΩ, ±1 %, which means 9.9 to 10.1 kΩ.

How do you read a 3 band resistor?

Three bands are two digits and a multiplier, with no tolerance band, and IEC 60062 gives a missing tolerance band ±20 %. Red-red-orange is 2, 2, times 1,000 = 22 kΩ ±20 %, anywhere from 17.6 to 26.4 kΩ. Choose 3 bands on the calculator and tap the colours.

How do you read a 4 band resistor?

Put the gold or silver band on the right. Band 1 and band 2 are digits, band 3 is the multiplier (how many zeros, or gold = divide by 10, silver = divide by 100) and band 4 the tolerance. Yellow-violet-red-gold is 4, 7, times 100 = 4,700 Ω = 4.7 kΩ, ±5 %: 4,465 to 4,935 Ω.

What does the tolerance band mean?

It is how far the real resistance may sit from the marked value when the part is new. Gold is ±5 %, silver ±10 %, brown ±1 %, red ±2 %, green ±0.5 %, blue ±0.25 %, violet ±0.1 %, orange ±0.05 %, yellow ±0.02 % and grey ±0.01 % (IEC 60062:2016). The calculator turns it into a range: 4.7 kΩ ±5 % is 4.465 to 4.935 kΩ.

What is the resistor color code formula?

Resistance = the digit bands read as one number × the multiplier, where the multiplier is 10 to the power of the band's number (black 1, brown 10, red 100 … gold 0.1, silver 0.01). The range is resistance × (1 ± tolerance / 100). For 4 bands: (10 × d1 + d2) × 10^m; for 5 and 6 bands: (100 × d1 + 10 × d2 + d3) × 10^m.

Sources

The colour code, multipliers, tolerances and temperature coefficients are those of IEC 60062:2016, the E series those of IEC 60063 and the SMD table that of EIA-96, each read from a public description on 2026-10-19: Electronic color code, E series of preferred numbers and Resistor: EIA-96 marking.