An old range chart yo might like.

[Leoz]

An old range chart you might like for periscope work. It assumes your mod uses the realistic x 1.5 and x 6 zoom settings on the scope.

Some years ago, I manually recreated it from an old rough looking German one.
I don't know German but you can deduce enough from it.

I find it handy. Example if you have the typical 140m long freighter in the game you can deduce range by how many degrees it occupies in the scope when looking at it 90 AOB.

Note the bottom comment where you can do some fuzzy math in your head if the AOB has not reached 90 yet.

If you are new to this sort of thing, recommend practicing with it in the u-boat school built into the game.

I have not used other games like U-Boat, but if it has the proper 1.5x and 6x zoom settings on the scope it should be good.

If you are a modder of course feel free to use it in your mods.

I just print it out to have it handy. Good hunting.