Quote from: hosseinimr93 on May 05, 2022, 01:39:29 PM

Quote from: NeuroticFish on May 05, 2022, 01:04:43 PM

Unfortunately I don't know of a tool that calculates it well how much you should pay for that new tx.

It's not difficult to do the calculation.

S_A = Size of the unconfirmed transaction
S_B = Size of the new transaction (the transaction you will make for doing CPFP)

f_A = The fee rate used for the unconfirmed transaction.
f_B = The fee rate you should use for the new transaction.
f = the fee rate required for a fast confirmation.

f_B = (f*(S_A+S_B) - S_A*f_A) / S_B

I'm sorry hosseinimr93 but I don't really understand your formula.

CMIIW but
SA*fA is the fee paid for the first transaction.
f*(SA+SB) is the fee to be paid for a fast transaction with a length of the 2 ones.

So
f*(S_A+S_B) - S_A*f_A
means you won't pay "again" the fee of the first transaction but only the fee for a fast transaction with a length of the 2, when they'll be mined.
S_A*f_A + f*(S_A+S_B) - S_A*f_A = f*(S_A+S_B)

For me, this fee is OK, it's the fair price IMO. I don't understand why you want to divide this fee by the length of the new transaction.