2.4 MΩ resistor colour code

redyellowgreengold

2.4 MΩ ±5%

red yellow green gold — four bands, read from the end with the bands closest to it.

Reading it

The two digit bands give 24 and the multiplier band multiplies it by 100,000:

24 × 100,000 = 2.4 MΩ

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 2.4 MΩ ±5% resistor is in specification anywhere from 2.28 MΩ to 2.52 MΩ. A meter reading of 2.28 MΩ on this part is not a fault and not a reason to replace it.

2.4 MΩ 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 2.4 MΩ reads

redyellowblackyellowbrown

— red yellow black yellow brown. The digits become 2, 4 and 0, and the multiplier drops one decade to yellow to compensate. The brown final band is ±1% rather than ±5%, which narrows the range to 2.38 MΩ–2.42 MΩ.

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 2.4 MΩ 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.

The quarter-watt part is the one in everybody's drawer: at 2.4 MΩ it will carry 323 µA or stand 774.6 V across it, and not both at once — those are the same limit expressed two ways.

2.4 MΩ exists only at ±5%

2.4 MΩ is an E24 value that is not in the E12 series, so it is made at ±5% and tighter but not at ±10%. That is why it is missing from cheap assortment boxes, which are usually E12 only — and why a design that calls for 2.4 MΩ is harder to service from a beginner's drawer than one that calls for 2.2 MΩ.

The nearest E12 value is 2.2 MΩ, 8.3% away, which is inside the ±5% band of neither part but close enough to substitute in most non-critical positions.

The same resistor as a surface-mount marking

Surface-mount resistors have no room for bands, so they carry printed digits instead — and 245 is what 2.4 MΩ 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.

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 245 and 2404 are the same 2.4 MΩ. 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 2.4 MΩ turns up

Megohm values are for very slow timing, for bleeding charge off a capacitor after power-down, and for keeping a high-impedance input from floating. Currents here are in microamps, so the resistor dissipates almost nothing and the limiting factor is the voltage across it rather than the heat in it.

Frequently asked questions

Nearby values

• 2.7 MΩ resistor colour code — red violet green gold
• 3 MΩ resistor colour code — orange black green gold
• 3.3 MΩ resistor colour code — orange orange green gold
• 3.6 MΩ resistor colour code — orange blue green gold
• 3.9 MΩ resistor colour code — orange white green gold
• 4.3 MΩ resistor colour code — yellow orange green gold
• 4.7 MΩ resistor colour code — yellow violet green gold
• 5.1 MΩ resistor colour code — green brown green gold
• 5.6 MΩ resistor colour code — green blue green gold
• 6.2 MΩ resistor colour code — blue red green gold

Every E24 resistor colour code · Wire gauge · Battery sizes