Only registered Republicans in the state of Iowa can participate in the Republican caucus. Individuals may register to vote as a Republican at the caucus.

Monday 1 February 2016 (presumably): Iowa Precinct Caucuses. Delegate Selection: Proportional Caucus/Convention. Voter Eligibility: Closed Caucus/Convention.

Precinct Caucuses
Source: Republican Party of Iowa.
Status: Official. Retrieved: Wednesday 3 February 2016.
Included in Nationwide vote.

Monday 1 February 2016 (presumably): Republican Party Precinct Caucuses meet in each precinct at 7:00 pm CST. Each Precinct Caucuses chooses the precinct's delegates to the County Convention and conducts a Presidential Poll by secret ballot.

Delegates are proportionally allocated to Presidential contenders based on the statewide vote. Each candidate receives (candidate's statewide vote) × 30 ÷ (total statewide vote) delegates. Round fractions to the nearest whole number. If there are too few delegates allocated, the candidate nearest the rounding threshold receives the additional delegate. If too many delegates are allocated, the candidate furthest the threshold looses a delegate. [Bylaws Article VIII]

The Iowa Republican Party report a turn out of 187,000.

Precinct Caucuses
Source: Republican Party of Iowa.
Status: Official. Retrieved: Wednesday 3 February 2016.

Cruz: 30 delegates × 51,666 ÷ 186,932 = 8.292 delegates. Round to 8.
Trump: 30 delegates × 45,429 ÷ 186,932 = 7.291 delegates. Round to 7.
Rubio: 30 delegates × 43,228 ÷ 186,932 = 6.937 delegates. Round to 7.
Carson: 30 delegates × 17,394 ÷ 186,932 = 2.791 delegates. Round to 3.
Paul: 30 delegates × 8,481 ÷ 186,932 = 1.361 delegates. Round to 1.
Bush: 30 delegates × 5,238 ÷ 186,932 = 0.841 delegates. Round to 1.
Fiorina: 30 delegates × 3,485 ÷ 186,932 = 0.559 delegates. Round to 1.
Kasich: 30 delegates × 3,474 ÷ 186,932 = 0.558 delegates. Round to 1.
Huckabee: 30 delegates × 3,345 ÷ 186,932 = 0.537 delegates. Round to 1.
Christie: 30 delegates × 3,284 ÷ 186,932 = 0.527 delegates. Round to 1.
Christie, furthest from the rounding threshold (0.473), looses a delegate.

Iowa's National Convention delegates are bound for the 1st ballot unless only 1 candidate is nominated at the Republican National Convention. In that case, Iowa's delegates are bound to vote for that candidate on the first ballot providing that candidate received votes in the Precinct Caucuses.

Saturday 12 March 2016 (presumably): Republican Party County Conventions convene in each county to choose delegates to the Congressional District Conventions and the State Convention.

Saturday 9 April 2016 (presumably): Republican Party District Conventions convene in each congressional district to choose the state's district delegates to the Republican National Convention according to the results of the Precinct Caucuses. Each of Iowa's 4 congressional districts is assigned 3 National Convention delegates.

Saturday 21 May 2016 (presumably): The Iowa State Republican Convention officially convenes. 15 of 30 National Convention delegates are selected according to the results of the Precinct Caucuses.

• The State Convention as a whole chooses Iowa's statewide delegates (10 base at-large delegates plus 5 bonus delegates) to the Republican National Convention.

In addition, 3 party leaders, the National Committeeman, the National Committeewoman, and the chairman of the Iowa's Republican Party, will attend the convention as pledged delegates by virtue of their position.