How to calculate net change
You can calculate net change by subtracting the current day’s closing price for an asset from the closing price of the previous day. For example, if company ABC’s stock closes at $125 per share today – after closing at $130 the previous day – then there has been a negative net change of $5 and you might decide to go short.
If, however, the price had increased to $135, up from $130 yesterday, then there has been a positive net change of $5. In this case, you might decide to take a long position.