When To Test is a free online calculator that lets individuals and leaders of large organizations input their data and receive a detailed plan for COVID-19 testing and prevention.

When To Test is a free online calculator that lets individuals and leaders of large organizations input their data and receive a detailed plan for COVID-19 testing and prevention.

What you need to know

Widespread mask usage, social distancing, and the availability of COVID-19 vaccines have gone a long way toward reducing the spread and impact of COVID-19. Still, many large organizations have struggled to come up with COVID-19 prevention and testing strategies suited to their particular needs. And for individuals, it’s not always clear when it’s important to get a COVID-19 test and when a test may not be necessary.

Now researchers have developed a tool to help people and organizations of all sizes know when to test employees — and themselves — for COVID-19.

What did the researchers do?

When To Test is a free interactive tool that lets individuals, school administrators, and leaders of large organizations customize testing strategies according to their risk.

For individuals, the calculator asks users to provide basic information such as location, vaccination status, mask usage, contact with other people, and recent COVID-19 testing history. Based on these factors, the calculator shares the individual’s risk of having, getting, and spreading COVID-19 and advises on whether they should be tested.

For schools and businesses, organization leaders provide the number of people on site at the organization, describe their ability to track down people who encounter an infected person, and estimate the number of employees who are vaccinated and those who wear masks consistently. Using those numbers, When To Test provides a list of tests that administrators should implement, how often the tests should be administered, and how much each testing plan would cost.

The project behind When To Test was funded by the National Institute of Biomedical Imaging and Bioengineering through the Rapid Acceleration of Diagnostics (RADxSM) initiative. It was developed by researchers at the Massachusetts Institute of Technology’s Institute for Data, Systems, and Society and the Consortia for Improving Medicine with Innovation & Technology. The site also offers detailed guides to implementing testing plans, allows users to compare the sensitivity and specificity of different tests, and helps users find trusted testing supplies.

Why is this tool important?

People and employers who have a solid COVID-19 testing plan in hand can take steps to avoid more of the major disruptions to their lives and their work that were costly for so many in the early stages of the pandemic. When To Test provides support with that decision-making process. By using the calculator, people and large organizations can also help maintain low rates of infection in their communities, keeping everyone safe.

Where can I go to learn more?

When To Test

  • The When To Test Calculator is a decision-support tool that lets individuals and large organizations plan for COVID-19 testing and reduce the spread of COVID-19.

Project N95

  • Project N95 is the National Critical Equipment Clearinghouse for personal protective equipment (PPE), COVID-19 diagnostic tests, and critical equipment. Supplies are available for purchase on the organization’s website.

Connect to Test

  • Connect to Test helps organizations and individuals find the right COVID-19 tests for their unique needs. Developed in collaboration with When To Test and Project N95, Connect to Test allows users to make informed and speedy COVID-19 testing decisions.


News and Stories

Read stories about the efforts underway to prevent, detect, and treat COVID-19 and its effects on our health.

NIH COVID-19 Resources by Topic

COVID-19 research information and resources by topic from NIH institutes and centers

Page last updated: November 22, 2021