Terrestrial carbon storage is dramatically decreased during glacial periods due to cold temperatures, increased aridity, and the presence of large ice sheets on land. Most of the carbon released by the terrestrial biosphere is stored in the ocean, where the light isotopic signature of terrestrial carbon is observed as a 0.32-0.7 parts per thousand depletion in benthic foraminiferal delta C-13. The wide range in estimated delta C-13 change results from the use of different subsets of benthic delta C-13 data and different methods of weighting the mean delta C-13 by volume. We present a more precise estimate of glacial-interglacial delta C-13 change of marine dissolved inorganic carbon using benthic Cibicidoides spp. delta C-13 records from 480 core sites (more than 3 times as many sites as previous studies). We divide the ocean into eight regions to generate linear regressions of regional delta C-13 versus depth for the Late Holocene (0-6 ka) and Last Glacial Maximum (19-23 ka) and estimate a mean delta C-13 decrease of 0.38 +/- 0.08 parts per thousand (2 sigma) for 0.5-5km. Estimating large uncertainty ranges for delta C-13 change in the top 0.5 km, below 5 km, and in the Southern Ocean, we calculate a whole-ocean change of 0.34 +/- 0.19 parts per thousand. This implies a terrestrial carbon change that is consistent with recent vegetation model estimates of 330-694 Gt C. Additionally, we find that a well-constrained surface ocean delta C-13 change is essential for narrowing the uncertainty range of estimated whole-ocean delta C-13 change.