When pump sizing, there could be many different type of flow meters, vortex, orifice, coriolis, magnetic etc.
Question is how process system engineer estimate the flow meter reasonalbe pressure drop ?
Pretty standard differential pressure transmitter ranges are 0-50, 0-100, and 0-200 inches of water column. 200 inches is roughly 7.23 psi. Practically, you'll probably want to have about half the dP of the transmitter at design flowrate, and often about half of the induced pressure drop is recovered downstream of the orifice. I concur with Sean's answer - allow for 2-3 psi.
I've used some inexpensive paddle wheel flowmeters on water with fairly signficant DPs (about 9-10psi in a 1" line), but the device's spec sheet clearly provided a pressure loss table.
Magmeters are line size with negligible DP loss.
Pitot tubes create less DP than an orifice plate, but with a resulting lower useable DP range.
I don't have a sizing program, but when DP loss has been an issue, I've asked the vendor to run the calculation and tell me what the calculate 'permanent pressure loss' value is. They always do.
For pump sizing allow 200 mbar permanent pressure drop for an orifice flow meter. That is about 2-3psi as mentioned above. They actually come in at 60-120 mbar permanent pressure drop.