most of the UPS makers (APC-Eaton/Dell-CyberPower-Emerson) have online calculators to determine the required UPS wattage/runtime
https://www.apc.com/shop/us/en/tools/ups_selector/
https://www.apcguard.com/Smart-UPS-Runtime-Chart.asp
https://www.cyberpowersystems.com/tools/runtimes/