Calculating resistance in decibel
Decibels (dB) represent a dimensionless ratio.  There is no way to express Ohms or any other non-dimensionless quantity in dB directly.  You can express a ratio of any value in dB, since that is always dimensionless.

In some cases, specific numeric scales have been created based on dB with 0 dB defined as some particular value.  That is the same as saying representing the ratio of the actual value to the reference value in dB.  For example, dBm is a common unit used in RF, with 0 dB representing 1 mW of power.  This is the same as saying that dBm expresses the ratio of some power to 1 mW.

In addition, dB is meant to express a power ratio.  It's basic definition is 10 Log10 (power1/power2).  Since power is proportional to voltage squared, dB is sometimes thought of as 20 Log10(volts1/volts2).  Since resistance does not relate in a direct way to power, there is no easy way to scale the ratio of two resistances to be meaningful in dB.  For example, if it were implied that the voltage is kept constant, then you could use -10 Log10(R1/R2), whereas if the current were kept constant then it would be 10 Log10(R1/R2).

So in short, there is no unambiguous way to express resistance in dB without some additional previously agreed upon convention.  Basically this is a bad idea since it only invites confusion.