Capacity for Care (C4C) / Magic Number Calculator

Last updated: 2016-05-24
Authors: Dr. Kate Hurley, Dr. Cynthia Karsten
Document type: Tools/Forms
Topics: Shelter Design and Housing, Shelter Population Management
Species: Feline

How many lives can your shelter save? The Capacity for Care / Magic Number Calculator helps you find out. This data-based spreadsheet app was revealed at the Million Cat Challenge - Where the Rubber meets the Road presentation at the 2016 HSUS Animal Care Expo. Here you'll find the calculator, plus notes on how to use it to make life better for shelter animals and shelter staff.

This calculator is meant to be used on a monthly basis to plan pathways, housing and staffing based on historical/expected intakes, outcomes and target length of stay (LOS).  It also allows you to take a moment to step back and see what is really happening at the shelter on a monthly basis, something that is not always easy when you are in the thick of it and trying to get through the day. 

The hope is that using this calculator will make population management decisions clearer and easier to make leading to a healthier, happier cat population and just as importantly, healthier, happier staff!

Please feel free to take it for a test drive and let us know how it works out for you by emailing us at

Some shelters find it easier to calculate their adoption driven capacity (number of animals to have up for adoption for a target length of stay) and work from there to define their overall capacity for care.  Turns out we have a calculator for that too!

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