As Tidal said, it will affect the mash pH so minimally, it won't really matter what you put it in as (it's not a roast or a crystal, and if you fiddle around with the other options, you'll see they have very little difference between them).
treat rye malt like wheat malt in these calculators. Based on my experience it has a similar distilled water pH to wheat, which is around 6. If rye is only a small portion of the grist it will matter little, though.