SRK formula used to calculate power of IOL is ( A ⇒ IOL constant ,K ⇒corneal curvature, L  ⇒ axial length of eyeball)
SRK formula to calculate power of IOL
Power = A → IOL constant
L ⇒ axial length of eyeball given by A - scan USG
K ⇒ Corneal curvature by Kertometer.
A - 2.5k - 0.9 L
A - 2.5L - 0.9 k
2.5A - L- 0.9K
L - 0.9L - 2.5K