The Semidiameter of a celestial body such as the Sun, Moon, or a planet, is his apparent equatorial radius expressed as an angle.
The general formula is S = S0/Δ
With:
S semidiameter
S0 the body's semidiameter at unit distance (1 AU)
Δ the body's distance to the Earth in AU.
For the Sun S0=15'59".63 = 959".63
Current Sun distance UA
Semidiameter of the Sun "
For the Moon S0=2".396
Current Moon distance UA
Semidiameter of the Moon "
