In President Obama’s last year in office, the United States dropped 26,172 bombs in seven countries, as the Council on Foreign Relations assesses. This estimate is undoubtedly low, considering reliable data is only available for airstrikes in Pakistan, Yemen, Somalia, and Libya, and a single “strike,” according to the Pentagon’s definition, can involve multiple bombs or munitions. In 2016, the United States dropped 3,028 more bombs—and in one more country, Libya—than in 2015.
Most (24,287) were dropped in Iraq and Syria. This number is based on the percentage of total coalition airstrikes carried out in 2016 by the United States in Operation Inherent Resolve (OIR), the counter-Islamic State campaign. The Pentagon publishes a running count of bombs dropped by the United States and its partners, and we found data for 2016 using OIR public strike releases and this handy tool. Using this data, we found that in 2016, the United States conducted about 79 percent (5,904) of the coalition airstrikes in Iraq and Syria, which together total 7,473. Of the total 30,743 bombs that the coalition dropped, then, the United States dropped 24,287 (79 percent of 30,743).

source: cfr.org