Definitions for "Allocable Costs"
Allocable Costs are those Allowable Costs that actually benefit grant or contract activities to which they are being assigned. In effect, Allocable Costs is another term for Direct Costs, since Indirect Costs, by definition, are excluded from being Allocable Costs.
According to the criteria set out in OMB A-21, a cost is allocable to a sponsored agreement if: It is incurred solely to advance the work under the sponsored agreement, It benefits both the sponsored agreement and other work of the institution, in proportions that can be approximated through use of reasonable methods, or It is necessary to the overall operation of the institution and is deemed to be assignable in part to sponsored projects
Project costs that are assignable or chargeable to one or more costs objectives in accordance with the relative benefits received or other equitable relationships defined or agreed upon by contractual parties.  For example, allocating a percentage of salary to several accounts.