Let me correct your figures......Lets talk about Jan 2011
Total number of aircrafts in IAF inventory
Mig-21 bison=121, Mig-29=69, Su-30MKI=122, Mirage 2005=51, Mig-27=145, Jaguar=139
Total number of aircrafts = 647 i.e @20 aircrafts = 32.7 squadrons
(all figures are approximate, still very close...