We apply a new technique to infer anthropogenic carbon (Delta-DIC) concentrations to WOCE CFC12 data from the Indian Ocean. In contrast to several recent studies the technique makes no assumptions about transport being dominated by bulk advection and does not require separation of the small anthropogenic signal from preindustrial carbon. Mixing is included implicitly by using CFC12 data to constrain "transit time distributions" (TTDs) from the outcrop to interior points of an isopycnal. The time-varying signal of Delta-DIC at the outcrop is propagated directly into the interior by the constrained TTDs. We have tested the TTD approach in an idealized model, where it proves to be more accurate than techniques relying on single tracer "ages." The bounds inferred for the Indian Ocean Delta-DIC distribution are similar in shape to CFC12, but Delta-DIC has penetrated more deeply. We obtain inventory bounds of 13-19 Gtons of anthropogenic carbon in the Indian Ocean north of 35S. The range is consequence of the incomplete constraint on the TTD provided by CFC12, and represents the natural uncertainty of Delta-DIC inferred from a CFC tracer.