Apparatuses, methods, and systems are disclosed for power headroom reporting for multiple uplink carriers. One apparatus includes a transceiver that receives a configuration of a plurality of uplink carriers for a serving cell. The first apparatus includes a processor that calculates a power headroom (“PH”) for each uplink carrier of the plurality of uplink carriers on the serving cell. The processor transmits (via the transceiver) a Power Headroom Report (“PHR”) based on the calculated PH for the plurality of uplink carriers of the serving cell.