Many Bitcoins are lost, it's hard to calculate how many.
How is the formula for calculating the lost Bitcoin?
You can estimate lost bitcoins by very long time inactive UTXOs, but it's estimation and it's not accurate number for actual lost bitcoin. Inactive Bitcoin UTXOs many years ago can turn to be active and these coins are not lost bitcoins.
You can use HOLD waves and make your estimation.
https://www.bitcoinmagazinepro.com/charts/hodl-waves/Lost Bitcoin: 3.7 million Bitcoin are probably gone forever. You can uncertainty in the article title, it's "probably gone forever".
Thank you, very interesting stuff: the hodl-waves, i agree it seems an estimated guess. In every wave-layer there must be a fraction of lost coins, but in older waves the fraction should increase, because of time en e.g. innovation in storage and increasing value of bitcoin. However the function of the wave >10y is constantly increasing in time(if you turn the wave), this pattern is different for ALL the other waves.
I suggest the wave >10y is significant different, maybe statistical analyses of the waves can determine the lost fraction with a high probability, Thanks again for advice, i will look at it.