# Minimum Blank Size

### Information

Minimum blank size (MBS) is used to determine if a patient requires a stock or grind lens. This is required to quote the patient appropriately

To calculate MBS, calculate Frame PD. $$Frame PD = Frame Size + Frame DBL$$

From this, Decentration as the difference between half the Frame PD and Monocular PD. $$Decentration = \left \lvert \frac{Frame PD}{2} - Monocular PD \right \rvert \\$$

Finally, MBS is calculated by adding Effective Diameter and an arbitary 2mm is added to compensate for lens bleed. $$Minimum Blank Size = Decentration + Effective Diameter + 2$$