If you are looking for a standstill calculator for use where the procurement is regulated by the the Public Contracts Regulations 2015 then you need to use the previous version of the standstill calculator, still available here.
The key change to the standstill period under the Procurement Act 2023 is that the period is now eight working days beginning with the publication date of the notice that commences the standstill period. This will usually be a Contract Award Notice, but could be a Contract Change Notice (see our Notices Generator to learn more).