There are no current formula for bitcoin prices due to its volatility and increasing number of holders. The basic knowledge of supply and demand only give you a glimpse of what are the factors that affects Bitcoin's prices. Also, take in consideration such parameters in relation to Bitcoin's price change: exchanges hacks, whales, forks, pump and other stuffs. Therefore, you can't actuate the price at any given time by the use of equation but you can relatively estimate where the prices would be by looking at the chart and analyzing it.