Am I Calculating Magi correctly? re: Self Employment Tax - do I add or subtract that amount?

Hi,

 

If I take an AGI, say around 20k...........and have Self employment tax of around 4k.......... from what I understand you take the AGI and add in 50% of the SE Tax to get MAGI right? you don't deduct the 50% of the SE tax...

 

So MAGI would be 22k not 18k? for ACA healthcare MAGI calculations?

 

Just making sure I'm supposed to add SE tax at 50% to AGI to get MAGI not subtract thanks!