What I've read is that the two planets, when they are closest to each other during the current conjunction, will be just 1/5 of the moon's diameter apart from each other.
Jupiter and Saturn are getting closer, as they near their once-in-20-years conjunction on December 21, 2020. At their closest, they'll be only 0.1 degrees apart. That's just 1/5 of a full moon diameter. Start watching them now, and you'll see them draw close together.
Before the end of 2020, great conjunction of Jupiter and Saturn | Astronomy Essentials | EarthSky