With Justice Antonin Scalia’s recent death, the age and health of sitting Supreme Court justices has again come into the spotlight. The average age of the eight justices currently on the court is a little more than 69 years old; Justices Anthony Kennedy, Ruth Bader Ginsburg, and Stephen Breyer are all older than 75. In addition to the Scalia seat, which may remain vacant due to GOP vows to block any Obama nominee, how many justices will the next president—whoever he or she may be—need to replace before Inauguration Day 2021?

We ran the numbers, based on Centers for Disease Control life tables, to measure the likelihood of the court losing more justices to the inevitable fate that we all face in the next few years. These tallies are approximations; for our purposes, we are treating Ginsburg, for example, as an average 82-year-old non-Hispanic white woman, rather than a relatively wealthy person (which might increase her life expectancy) or a cancer survivor (which might decrease it). We’ve put the probabilities together into a tool that lets you combine justices however you want: You can calculate the probability of the court losing two liberal justices, of the court losing another conservative justice, or of the court losing Justice Kennedy (however you label him). You can also combine them in any scenario you want.

If you needed any more evidence of how important this election will be toward determining the future of the Supreme Court, this tool should supply it.