That means for 20 transactions, single payment 20 times in fee will be 20 times higher. But if I send to 20 addresses at ones, the fee can only increase 3 to 4 times due to the transaction size. This is still lower.
I think you misunderstood me.
Sending 20 single transactions with 1 input / 1 output each, costs 3-4 times more than sending a single transaction with 1 input / 20 outputs.
If you play with the
site linked by Lucius:
1 input / 1 output:
~138 vbytes 20x 1 input / 1 output:
~2760 vbytes1 input / 20 outputs:
~784 vbytes What matters is the size of the transaction, not the actual amount been sent.
Correct.
And the size is determined by the amount of inputs/outputs and the address type (are you using legacy, multisig, segwit, ..).