Actually there is no formula. Have you ever found 100% correct Bitcoin price prediction? No, so there is no formula.
I do not know if there is a formula for the price of bitcoin but I once heard that the price of bitcoin is usually controlled by market whales. These are the reasons for the price fluctuations By analyzing every price man, they increase the price.
Whales can manipulate with the market, it's not a secret. Market manipulations are a common thing on every market, crypto market is maybe more vulnerable because low market cap (generally it's low, 180B is a bitcoion market cap, if group of whales get together with just 10% of that they can manipulate with the market).
With so many manipulations from whales, groups that get together, independent traders, trading bots, with 24/7 market that never sleeps its impossible to create a formula for predicting the price movement. Changes can happen while you sleep, and I mean big changes. Fluctuations in crypto market are so high that you can either earn from them in short term, or to simply believe in the future of some projects and just hold.