The latching current of an SCR is 12 mA. Its holding current will be
The ratio of latching current to holding current for an SCR does generally fall in the range of 2.5 to 3.
Based on this ratio, if the latching current of an SCR is 12 mA, then a rough estimate of the holding current can be calculated as follows:
Holding current = Latching current / 2.5 to 3
Holding current ≈ 4 to 4.8 mA
So, in this case, an estimate of the holding current based on the given latching current of 12 mA would be in the range of 4 to 4.8 mA.