Gerrymandering is the drawing of political districts to gain advantage beyond what would accrue by natural patterns of population. Gerrymandering can benefit an individual legislator or a whole political party. This site is principally concerned with partisan gerrymandering, the establishment of an overall advantage across an entire state.

Partisan gerrymandering is considered justiciable by the United States Supreme Court, but a nationwide standard has not been established. Below are online calculators for simple statistical tests described in "Three Tests for Practical Evaluation of Partisan Gerrymandering," by Samuel S.-H. Wang, 68 Stanford Law Review 1263 (2016). This approach was awarded a prize in Common Cause's 2016 First Amendment Gerrymander Standard Writing Competition.


Step 1: Pick a data set

Select a state and year, upload a file, or enter data manually.

Data should be one district per row.

One number per row will be interpreted as Democratic two-party vote share (%). Two numbers per row (separated by commas) will be taken as D and R vote share, rescaling to add up to 100% if necessary.

Use the same rule as Option 2.

Democratic Republican

Press Tab to move between columns

Step 2: Uncontested races

Step 3: Fantasy delegation parameters

Step 4:

Calculation may take up to 3 minutes.