^Richichi, A.; Roccatagliata, V. Aldebaran's angular diameter: How well do we know it?. Astronomy and Astrophysics, Volume 433, Issue 1, April I 2005, pp.305-312. "We derive an average value of 19.96±0.03 milliarcsec for the uniform disk diameter. The corresponding limb-darkened value is 20.58±0.03 milliarcsec, or 44.2±0.9 Rȯ."
^Richichi, A. and Roccatagliata, V. derived an angular diameter of 20.58±0.03 milliarcsec, which given a distance of 65 light years yields a diameter of 61 million km