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Quickfingersluc does not use this, he just estimates in his head.
When layering in, it's best to nibble small and increase the size of your buys as the price goes down. Then do the opposite when the price goes up, making your biggest sell at the highest price.
This video shows what to do with a small purchase.
Video: Using Excel to find average price paid for a coin on Coinigy
Excel file to calculate sell points
Hopes this helps those crypto-coin traders that need to know more precisely how they are doing.