How Is the “Cost to Attack” Typically Calculated for a PoW Cryptocurrency?

The "cost to attack" is typically calculated by determining the amount of hashrate required to achieve 51% of the network's total hashrate. This required hashrate is then multiplied by the current market rental price of that hashrate over a specific time period (e.g. one hour or one day).

This calculation provides the economic cost to launch a successful double-spending attack. The total hashrate of the network is the primary variable influencing this cost.