written usage for resistance values
of electronic resistors

Because it is very easy to miss decimal points (or decimal commas) in parts lists, a convention for writing resistances has developed. By this convention, which is not approved by the IEC or the British national standards, the decimal point is replaced by the letter “K” (for thousand) or “M” (for million). So, for example

47,000 = 47K  
4,700 = 4.7K = 4K7
4,700,000 = 4.7M = 4M7

Less frequently encountered is the use of the letter “R” where the multiplier is 1 or less. The symbol Ω was not used because it is not available on many printers. For example:

0.68 = R68 (multiplier is 0.01, silver)
6.8 = 6R8 (multiplier is 0.1, gold)
68 = 68R (multiplier is 1, black)

British Standard BS1852

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