Determining the correct power of the intraocular lens (IOL) forms the most important factor affecting the patient satisfaction after surgery.The axial eye length (AEL) measurement is the main step in intraocular lens (IOL) power calculation. The immersion ultrasound technique is more accurate than the contact method for AEL measurement. In difficult cases, the use of a combination of A- and B- scan techniques for the AEL measurement is recommended. Also, the optical biometry is an excellent, simple non-contact and the most accurate method. Keratometry can be done by the manual keratometer, automated keratometer or corneal topography in cases of abnormal keratometry. The Pancorneal slit-scanning topography and the Pentacam eye scanner are the most accurate keratometry devices. The third (Holladay I, Hoffer - Q and SRK-T) and fourth (Haigis and Holladay II) generations formulas are the most accurate and should be used. The spherical equivalent change, the feiz nomogram, the no-history, the modified Maloney and the Haigis method are the recommended methods to calculate the conreal power after keratorefractive surgery.