Resistors - Why are some values expressed as a decimal and others using a R?

Thread Starter

applearcher

Joined Apr 21, 2019
6
Noob here, learning lots everyday. I googled my question, but didn't come up with anything. Probably due to my lack of correct terminology.

Why are some resistor values expressed as a decimal i.e., .1, .33 and others are expressed using an R 0R3, 0R5, 2R7?
 

MrChips

Joined Oct 2, 2009
21,911
It is very easy to miss a decimal point on components and printed documents.
The convention adopted is to place R, K, or M where the decimal place belongs.

0R3 = 0.3Ω
2R4 = 2.4Ω
4K7 = 4.7KΩ
2M2 = 2.2MΩ

Similarly, for capacitance
5p6 = 5.6pF
0n1 = 100pF = 0.1nF
4n7 = 4.7nF
 

djsfantasi

Joined Apr 11, 2010
6,850
Perfect, Thank you. If I understand correctly, 1MR25 would be 1.25MΩ?
Or 1M25 is 1.25MΩ. The convention is to use one of the letters (depending on the magnitude of the value) in place of the decimal point. Hence, 1MR25 is redundant. Do you mean 1.25Ω or 1.25MΩ?
 

crutschow

Joined Mar 14, 2008
25,462
Or 1M25 is 1.25MΩ.
To the TS:
Be sure you are aware of the letter case for M, since 1M25 is 1.25 megohm and 1m25 is 1.25 milliohm.
(Numerous newbies have had their Spice simulations puzzlingly fail because Spice doesn't pay attention to letter case, interpreting all letters as lower case, so M becomes milli. You must use meg for mega.)

The case of letters k, n, and p however, makes no difference, although by convention they are lower-case.
 
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