Though this may have been covered previously (I have not read all the entries on this forum), please know that Kovacs is the second most common family name in Hungary. It is second only to Nagy. The name means "smith," and just as with English names, there are thousands of families with this surname. Some of the families were noble; most were not. Yet there were hundreds of noble Kovacs families. There are descriptions or illustrations of many of their coats of arms available, but there is no one Kovacs coat of arms. As in all genealogy research, you must start from what you know and go backwards. If you can trace your family to an indication of nobility (normally noted in the church records), that is a step forward, but only a first step. You would then need to determine WHICH noble Kovacs family it is. In most cases this means identifying the geographical origin of the family, or who was ennobled and when, or connecting a known ancestor with one of the documented genealogies. For example, one Kovacs family originated in Jardanhaza, a village in Borsod megye. But the family was known in the 18th century in Bihar and Nograd megyes and limited genealogical tables are available up to the mid-1800s. You might find them listed as Kovacs (jardanhazai).
To complicate matters further, many families had aliases, and Kovacs was often used. Over time, a Kovacs might eventually become known by the other name, or vice versa. Name changes can be one of the most frustrating features of Hungarian genealogical research. My husband's great-grandfather, for instance, was known by three entirely different surnames (and two given names as well) in his lifetime. It took several years of research to discover this.
The more information you can gather, the greater the possibility that you may find "your" coat of arms. I enjoy helping people uncover their ancestral pasts, and sometimes being able to furnish coats of arms, but it is not possible to give you "the" Kovacs coat of arms.