Is there a calculation for exchange rate stability? Exchange rate stability can be used as an indicator to determine how consistently you will earn the same profit over a period of time when mining a cryptocurrency. My current thinking is that a chart of the daily average exchange rate values from the last 14 days can indicate the exchange rate stability of a coin based on exchange rate fluctuations in the last 14 days.

But I have no idea how to actually go about calculating a metric like this or what the units would be.
This site can help you calculate the beta of Bitcoin:

https://btcvol.info/

"What definition of volatility does btcvol.info use?

The standard deviation of daily returns for the preceding 30- and 60-day windows. These are measures of historical volatility based on past Bitcoin prices. When the Bitcoin options market matures, it will be possible to calculate Bitcoin's implied volatility, which is in many ways a better measure."

https://en.wikipedia.org/wiki/Beta_(finance)

In finance, the beta (β or beta coefficient) of an investment indicates whether the investment is more or less volatile than the market. In general, a beta less than 1 indicates that the investment is less volatile than the market, while a beta more than 1 indicates that the investment is more volatile than the market. Volatility is measured as the fluctuation of the price around the mean: the standard deviation.