For probably the most half, your pockets software program ought to maintain all this. You need to solely decide how urgently you want the transaction to be confirmed and choose the feerate, the pockets would maintain the remaining. The 88 you point out would possible seek advice from a feerate of 88 sats/vbyte right here, though that appears like a gross overestimate on the present market circumstances.
If you wish to manually construct a transaction, it’s good to know a bit extra.
Earlier than you construct a bitcoin transaction, you recognize which transaction outputs you might be aiming to create. The recipients addresses let you know how a lot information it will take to specify every output within the transaction. The transaction header can also be principally fixed dimension, it is 10 bytes for non-segwit transactions and 42 weight models for segwit transactions.
The enter facet is a little more sophisticated, as you often have no idea upfront what number of inputs it will take to fund your transaction. Your pockets may additionally be capable of spend Unspent Transaction Outputs (UTXOs) of assorted output sorts which take completely different quantities of information to incorporate in a transaction.
So, you will both want to select the inputs first, then decide their dimension and calculate the charges, or you are able to do each in live performance, by calculating the associated fee for every enter and deducting in from the UTXO’s values earlier than contemplating them for inclusion.
The precise sizes for some common output sorts will be seen on this desk: 
