Assuming you know the difficulty level, hash value, and mining reward
This has nothing to do with your transaction time.
how can you know how long the getting one confirm will take if you pay the average transfer fee (50%)? Even roughly ..
https://bitcoinfees.earn.com/ gives an estimate.
What I want to know is formula for calculating transaction time(getting one confirm time).
There is no "formula", it depends on other transactions and their fees.
Thank you.
But is there at least a reference number?
As you know, sometimes there has been a lot of change in transaction time due to recent large hash rate fluctuations.(cause of BCH..) Like in this situation, we need an objective formula to refer to.