Caucus Math in 3 minutes

Iowa Democratic Party
3 min readJan 31, 2016

Caucusing is fun, easy and important — and yes, there is math involved! That’s why we’re here — to help you get to the bottom of the math behind the Iowa Democratic Caucuses.

First things first — on Monday, February 1st, Iowa Democrats across the state will gather at nearly 1,700 precincts to make their preferences for the Democratic nomination for President. It’s a pretty big deal.

Presidential candidates are then awarded delegates based on the preference group’s size at each of the precinct locations.

That’s the easy explanation. Let’s dive in a little deeper to understand just exactly how delegates are awarded on caucus night:

Step 1: Precinct chairs count the number of eligible caucus goers.

Step 2: To be awarded delegates, candidates must have a minimum number of caucus attendees in his or her group. This is called viability. Precinct chairs will determine the viability threshold using these formulas:

  • If the caucus elects one delegate: The delegate is elected by a simple majority.
  • If the caucus elects two delegates: Viability is 25%
  • If the caucus elects three delegates: Viability is 16.66%
  • if the caucus elects four or more delegates: Viability is 15% →this is the viability at most of our caucus locations!

Step 3: Caucus goers will then get into preference groups and precinct chairs will ensure all of the groups are viable.

Step 4: If preference groups are not viable, caucus goers in those groups can realign and join a viable group, or pull people from other groups to become viable themselves.

Step 5: Once you are only left with viable groups, now it’s time to award delegates.

Here’s the formula:

(Number of people supporting your candidate) x (Number of total delegates the caucus is electing)


(Total number of people at the caucus)

Quick example: Your precinct elects 5 delegates. 100 people show up to caucus. Here is how people align:

Candidate A — 40 people (40x5/100=2 Delegates)

Candidate B — 35 people (35x5/100=1.75 delegates, round up to 2 Delegates)

Candidate C — 25 people (25x5/100=1.25 delegates, round down to 1 Delegate)

Step 6: Finally, sometimes the math can award too few or too many delegates. Then, here’s what happens:

  • If the total number of delegates is fewer than the number to be elected, an additional delegate is awarded to the group(s) with the highest decimal below 0.5.
  • If the total number of delegates is greater than the number to be elected, a delegate is subtracted from the preference group(s) with the lowest decimal above 0.5 — but a group can’t lose it’s only delegate.

There you have it. You have now learned about Caucus Math!



Iowa Democratic Party

The Iowa Democratic Party is dedicated to promoting Democratic principles across Iowa & electing qualified and dedicated candidates at all levels of government