1 Kiloquad = 1000 Quads
1 Quad = 4000 Iso-bits
Aside from this, the actual amount of memory in 1 kiloquad had not been defined meaningfully (as in terms of bytes) by the creators of the series. The reason the term was invented in the first place was to mask the data capacity of the futuristic computers of Star Trek, in anticipation that an actual description might appear foolish in the not-to-distant future as a result of advancing computer technology in the real world.
Later on, however, many r.a.st.tech contributors have converged on 1 kiloquad being equal to 1000 (kilo) * 1 quadrillion bytes, which becomes approximately equal to 1 petabyte or 1 billion gigabytes.