Quote from: MrsHash on April 04, 2017, 07:35:45 PM

Yes, I want to use fixed fee to guarantee that transaction will be confirmed in about 2-3 blocks.

This is why you should NOT use fixed fee.

You CANNOT guarantee that transaction will be confirmed in about 2-3 blocks if you use fixed fee, since you may have a very big transaction and miners might choose to ignore your transaction.

Confirmation time depends on how much fee you pay PER BYTE. If you use fixed fee, then the fee per byte will be small on big transactions (lots of inputs and/or outputs) and big on small transactions (only a few inputs and outputs). The only way you can guarantee that the fee will ALWAYS be enough with fixed fee would be to pay a ridiculously high fee on small transactions.

Better would be to use a proper fee per byte (or fee per kilobyte). Then you can provide the proper incentive to the miners so that they will be very likely to confirm your transaction in the next block or two.

Quote from: MrsHash on April 04, 2017, 07:35:45 PM

Because I actually wait up to 20 hours currently for some transactions to get confirmed.

Then you need a higher fee PER BYTE. You do NOT need a fixed fee.