If you are not proficient in calculating, you can still calculate if you are profitable even if you are losing money. You can still calculate from the difference in price when you buy and sell it 
I think Quite enough with the calculations. We all know that it is not the right thing to do. Even if he gets a little, it's just luck. Why not sell it a bit higher? or just HODL until the price goes up. Then sell higher than the original price. The business is bad if you keep doing it.
There is no profit if you sell for a price when you buy it. There is money lost if you do that. Always remember that there is a charge when you transfer so that the $ 100 you use will decrease if you sell it. You will only get a profit if the btc price will go up.