1.8 kΩ resistor colour code
browngreyredgold
1.8 kΩ ±5%
brown grey red gold — four bands, read from the end with the bands closest to it.
| Band 1 — first digit | brown = 1 |
| Band 2 — second digit | grey = 8 |
| Band 3 — multiplier | red × 100 |
| Band 4 — tolerance | gold ± 5% |
| Value | 1.8 kΩ |
| Acceptable range | 1.71 kΩ to 1.89 kΩ |
Reading it
The two digit bands give 18 and the multiplier band multiplies it by 100:
18 × 100 = 1.8 kΩ
Which end to start from is the part that catches people. The tolerance band is the one set slightly apart from the other three, and it is gold or silver far more often than not — neither of which is a digit colour, so a gold or silver band tells you which end you are at. Read from the opposite end.
What ±5% actually means
A 1.8 kΩ ±5% resistor is in specification anywhere from 1.71 kΩ to 1.89 kΩ. A meter reading of 1.71 kΩ on this part is not a fault and not a reason to replace it.
1.8 kΩ is one of the E24 values — the 24 steps per decade that ±5% resistors are made in. The steps are spaced so that the tolerance bands of neighbouring values just about touch: there is no gap between one value's range and the next, and no point making anything in between. It is the same reasoning that gives ±10% parts only 12 values per decade.
The same resistor with five bands
Precision resistors carry five bands: three digits, a multiplier and a tighter tolerance. The same 1.8 kΩ reads
browngreyblackbrownbrown
— brown grey black brown brown. The digits become 1, 8 and 0, and the multiplier drops one decade to brown to compensate. The brown final band is ±1% rather than ±5%, which narrows the range to 1.78 kΩ–1.82 kΩ.
How much this one can take
A resistor's limit is heat, not voltage or current on their own: the power it turns into heat is V² ÷ R, so the same wattage allows very different numbers at 1.8 kΩ than it does at a value ten times away. This is the part of a colour code lookup people actually came for and charts leave out.
| Rating | Maximum current | Maximum voltage |
|---|---|---|
| ⅛ W | 8.3 mA | 15 V |
| ¼ W | 11.8 mA | 21.2 V |
| ½ W | 16.7 mA | 30 V |
| 1 W | 23.6 mA | 42.4 V |
The quarter-watt part is the one in everybody's drawer: at 1.8 kΩ it will carry 11.8 mA or stand 21.2 V across it, and not both at once — those are the same limit expressed two ways.
1.8 kΩ is a ±10% value too
1.8 kΩ is one of the twelve E12 values as well as one of the twenty-four E24 ones, which means it is made at ±10% and ±5% both. In practice that makes it easier to find and cheaper: E12 values are what a beginner's assortment box contains, and a shop that stocks one range stocks this value.
The nearest E12 value is 1.8 kΩ — this one.
The same resistor as a surface-mount marking
Surface-mount resistors have no room for bands, so they carry printed digits instead — and 182 is what 1.8 kΩ looks like on one. The scheme is the colour code with the colours replaced by the digits they stood for: two significant figures and a count of zeros.
| Marking | Used on | Reads as |
|---|---|---|
182 | Three-digit, ±5% parts | 18 followed by 2 zeros |
1801 | Four-digit, ±1% parts | 180 followed by one zero |
A four-digit marking is not a different system, only a more precise one: it carries three significant figures instead of two and takes one off the zero count, which is why 182 and 1801 are the same 1.8 kΩ. If a board has both on it, the four-digit parts are the ±1% ones.
Very small ±1% parts use a third scheme, EIA-96, where two digits index a table of values and a letter gives the multiplier — 01C rather than 1002. It only covers the E96 series, so it has no marking for most of the E24 values on this site, and a marking with a letter in the middle is never one of these codes.
Where 1.8 kΩ turns up
Single-figure kilohms is the pull-up and pull-down decade. It is strong enough to hold a line firmly against leakage and weak enough not to fight whatever drives the line low, which is why 1 kΩ to 10 kΩ covers almost every pull-up ever specified.
Frequently asked questions
What is the colour code for a 1.8 kΩ resistor?
brown grey red gold on a four-band resistor: brown for 1, grey for 8, red for a multiplier of ×100, and gold for ±5%.
What resistor is brown grey red gold?
1.8 kΩ, ±5%. The first two bands are the digits 1 and 8, the third multiplies by 100, and the gold band is the tolerance.
What is the tolerance range of a 1.8 kΩ ±5% resistor?
1.71 kΩ to 1.89 kΩ. A resistor measuring anywhere in that range is within specification, which is why a meter reading of 1.71 kΩ on a 1.8 kΩ part is not a fault.
What is the five-band code for 1.8 kΩ?
brown grey black brown brown — three digit bands (1, 8, 0), then brown as the multiplier and brown for ±1%. Five-band resistors carry an extra significant figure, so the third digit is the zero that a four-band code leaves to the multiplier.
Nearby values
- 2 kΩ resistor colour code — red black red gold
- 2.2 kΩ resistor colour code — red red red gold
- 2.4 kΩ resistor colour code — red yellow red gold
- 2.7 kΩ resistor colour code — red violet red gold
- 3 kΩ resistor colour code — orange black red gold
- 3.3 kΩ resistor colour code — orange orange red gold
- 3.6 kΩ resistor colour code — orange blue red gold
- 3.9 kΩ resistor colour code — orange white red gold
- 4.3 kΩ resistor colour code — yellow orange red gold
- 4.7 kΩ resistor colour code — yellow violet red gold