Is this some sort of hypothetical question? Why are there so many questions on investing that seem to come from people who don't know the first thing about taxes, investing or anything else? For crying out loud, capital gain in the amount of money you sold the stock for less how much you paid for it. If you sold partial shares, you would account for the split, if you sold 180 shares at the current price you would compare that to 30 shares, 1/6 of the new number of shares.

"Easy answer" - assume the stock split 6-for-1. Take your basis / cost, and divide it by 6. That is your cost. Then take whatever the price you sell the stock for, and deduct your cost / basis. What is left is your gain - but remember to also deduct your commissions from your original purchase, and on your sale.

for days lol

When you calculate gains or losses on sale of stock, how do you determine this when stocks have split several times. For example, if stocks were originally 100 but now it's 600, how do you calculate the gains or losses if I decide to sell all 600 shares of stock.