This paper provides new estimates of the social discount rate (SDR), one of the key parameters used in the cost-benefit analysis framework to assign a present monetary value to costs and benefits occurring at different points in time and spreading over a long-term period. The paper draws upon work carried out in the framework of the ongoing H2020 Future Circular Collider Innovation Study to calculate an ad hoc SDR to be used in the socio-economic impact assessment of the Future Circular Collider (FCC). The countries selected for the purpose of this estimation were those contributing to CERN budget, including both EU27 Member States and non-EU Member States. Beyond providing a new estimate of SDR, this paper also discusses the impacts of COVID-19 pandemic crisis on the SDR by providing two different scenarios (before and after).