I don't carry a scale. I guesstimate the fish. I might tell whoever I'm with that it was "about" whatever if it was a good fish.
I kept one decent fish a few weeks ago because my wife was wanting fish. I guessed 25. I weighed it on a boga knock off before I filleted it. It was 23. The arm and eye scale isn't off by much more than 10%
I might pick up a Manley spring scale this fall, before the Gibby tournament starts, just so I know whether a big fish is worth keeping for the official scale---but it would have to become the leading fish.