Not really, the wallet will check its mempool every time you try to transact, and the calculations will be done instantly, there is probably no way to tell how much is it going to pay in the future.


As of right now and as the above user mentioned, fees have dropped, so yup with 145sat/byte is more than enough, your new transaction will be more or less of the same size, so you need to pay (current fees - 2.5sat/byte) * 2, to put this in a simple explanation, let's assume each transaction size is 10 bytes and current fees are 10 sat/byte so your total for this CPFP needs to be 10sat/byte*10bytes + 10sat/byte*10bytes= or a total of 2000 sats for the two, since you paid 2.5 sats /byte for the first one than you paid 2.5*10 = 25 sats/byte,  and thus the second transaction total fee must add up to 2000 sats and therefore 2000-25 =  1,975 sats, divide that by the transaction size it becomes 197.5 sats per byte which is what you have to pay on the child transaction for this to attract miners to take the transaction.

Now enough lecturing, your second transaction should be about 370 bytes , current best fees (as I type) is 40 sats/byte, the two transactions must have a total of 40*(370+370)= 29,600 sats, you already paid 930, so 29,600 - 930 = 28,670 sats, divide that by 370 you get 77 sats/byte for the new transaction.

Since it's unlikely that you are sitting there waiting for this post, you have to perform the same calculation and only replace the 40 sats/byte to whatever the current fees are.



They are in sat/byte.