COVID-19 Risk Calculator

During the COVID-19 pandemic, people around the world asked themselves the same question: What changes can we make to reduce the risk of COVID-19 transmission?

To help provide some insight into this question, the Harvard Healthy Buildings Program released this beta version of the ASIMI (Aerosol and Surface Interaction Model for Infectious diseases) Tool for calculating the risk of COVID-19 transmission, which estimates potential infection risk based on several factors and transmission pathways.

This tool is based on our peer-reviewed paper in the Proceedings of the National Academy of Sciences of the United States of America.

Please note: The following information was created in 2021/2022 and is not regularly updated. For the latest information on COVID-19, please refer to the Center for Disease Control and Prevention (CDC), or the World Health Organization (WHO).

1. Rooms & People

Basic

Advanced

Room Size 100 m² 1076 ft.²

Small

Large

The floor area of the room.

m²

ft.²

The height of the room.

ft.

Time Spent in Room 1 hour(s)

1 hour

10 hours

Total time spent in the room.

hours

Activity Type

Activity Type of the infected individual(s).

Breathing rate of susceptible individuals.

m.³/hour

cfm/hour

Help estimating breathing rate

Number of infected individuals in the room.

person(s)

2. Risk Reduction

Basic

Advanced

Face Cover Usage

Not Likely

Very Likely

Proportion of occupants wearing a face mask.

Proportion of occupants wearing a full face shield.

Type of mask used

Pathogens removed by the type of masks in use.

Personal Habits

Poor

Excellent

Probability of washing hands after touching surfaces.

Cleaning efficiency of hand washing.

% efficient

Average frequency at which people in the room touch surfaces.

touch/hr.

Average frequency at which people in the room touch their faces.

touch/hr.

How frequently two people in the room shake hands.

touch/hr.

Room Cleaning

Poor

Excellent

Probability of cleaning surfaces before the next use.

Pathogens removed by surface disinfection.

None

Perfect

Average percentage of time that susceptible individuals spend within six feet of potential infector(s).

% of total time

Natural Room Ventilation

Windows Closed

Windows Open

Natural ventilation or air infiltration rate of outdoor air into the room.

1/hr

HVAC System

Low

High

HVAC system supply/return rate.

1/hr

Removal efficiency of the HVAC air filter.

Operation time fraction of HVAC system.

Fraction of outdoor air in HVAC system supply air.

Stand-alone mechanical ventilation rate.

1/hr

Air Cleaning and UV Disinfection System

Poor

Excellent

Air cleaning rate.

1/hr

Air disinfection rate using UV irradiation systems.

1/hr

Results

Configure the calculator settings and then click the button below to generate your risk report.

Disclaimers and Terms of Use

Important: This tool is primarily designed to provide insight into the effectiveness of various control strategies and impacts of human behaviors on infection risks in indoor environments rather than providing exact estimates of absolute risk. It is based on several super-spreading events, which may result in overestimates of the risk that people face in typical indoor environments.

This COVID-19 Risk Calculator is provided for informational and educational purposes only. It is intended to offer guidance regarding best practices regarding the general operations of buildings in an effort to reduce the risk of disease transmission, specifically novel coronavirus SARS-CoV-2 and the disease it causes, COVID-19. Adherence to any information included in this tool will not ensure successful treatment in every situation, and user acknowledges that there is no “zero risk” scenario.

User acknowledges that each building and situation are unique and some of the guidance contained in the tool will not apply to all buildings or countries outside the United States. Furthermore, the tool should not be deemed inclusive of all proper methods nor exclusive of other methods reasonably directed to obtaining the same results.

The tool is in no way intended to override or supersede guidance from government and health organizations, including, without limitation, the Centers for Disease Control and Prevention, the World Health Organization, the United States Government, and or any States. The information contained herein reflects the available information at the time the tool was created.

User recognizes that details and information are changing daily, and new information and/or the results of future studies may require revisions to the tool (and the general guidance contained therein) to reflect new data. We do not warrant the accuracy or completeness of the guidance in this tool and assume no responsibility for any injury or damage to persons or property arising out of or related to any use of the tool or for any errors or omissions.

This tool is primarily designed to provide insight into the effectiveness of various control strategies and impacts of human behaviors on infection risks in indoor environments rather than providing exact estimates of absolute risk. It is based on several super-spreading events, which may result in overestimates of the risk that people face in typical indoor environments.

Please note that the risk estimates determined by this tool:

Assume at least one infector and one susceptible individual are present in the indoor environment,
Assume the infector(s) is/are at their peak infectivity,
Do not consider different levels of infectivity of the new variants of SARS-CoV-2,
Do not consider variation in individuals’ susceptibility (e.g., age, underlying diseases, and vaccination status change the susceptibility of individuals),
Assume that there is no residual risk of transmission from activity that occurred prior to the scenario input to the calculator, and
Are not applicable to children.

Important Notes About This Tool

The COVID-19 Transmission Risk Calculator is primarily designed to provide insight into the effectiveness of various control strategies and impacts of human behaviors on infection risks in indoor environments rather than providing exact estimates of absolute risk. It is based on several super-spreading events, which may result in overestimates of the risk that people face in typical indoor environments.

Please note that the risk estimates determined by this tool:

Assume at least one infector and one susceptible individual are present in the indoor environment
Assume the infector(s) is/are at their peak infectivity
Do not consider different levels of infectivity of the new variants of SARS-CoV-2
Do not consider variation in individuals’ susceptibility (e.g., age, underlying diseases, and vaccination status change the susceptibility of individuals)
Assume that there is no residual risk of transmission from activity that occurred prior to the scenario input to the calculator
Are not applicable to children