Buy American Improvement Act of 2013

Buy American Improvement Act of 2013 - Requires the Administrator for Federal Procurement Policy: (1) to promulgate regulations to standardize and simplify federal agency compliance with, and reporting on, Buy American requirements; (2) in developing Buy American  guidelines, to consider any significant decrease in U.S. employment resulting from the granting of waivers of Buy American requirements to be inconsistent with the public interest; and (3) to impose certain notice requirements on federal agency heads after receiving a request for a waiver and to require publication of the determination for why a waiver was granted.

Revises Buy American reporting requirements to require: (1) federal agencies to report to the Administrator, for the period FY2013-FY2018, on the amount of their acquisitions of articles, materials, or supplies purchased from entities outside the United States; and (2) the Administrator to submit to Congress a consolidated report on all agency reports received and make such report publicly available on a website.

Imposes limits on waiver determinations, including that a project cost determination will not be deemed unreasonable unless compliance with Buy American requirements causes an increase of overall project costs by more than 25%. Defines "substantially all" for purposes of Buy American requirements to mean that articles, materials, or supplies shall be treated as made substantially all from articles, materials, or supplies mined, produced, or manufactured in the United States if the cost of the domestic components of such items exceeds 75% of the total cost of all such items.

Requires the Comptroller General to report on the extent to which, in FY2009-FY2013, articles, materials, or supplies acquired by the federal government were manufactured, mined, or produced outside of the United States.

Requires this Act to be applied consistently with U.S. obligations under international agreements.