How it is calculated
Average cost is total cost ÷ total shares. For example, if you hold 100 shares at ₩10,000 and buy 50 more at ₩8,000, the average becomes (1,000,000 + 400,000) ÷ 150 ≈ ₩9,333.
The target-average mode solves (shares held × average + added shares × current price) ÷ (shares held + added shares) = target average for the added shares. The target must lie between the current price and your average cost, and the closer it is to the current price, the faster the required shares grow.
Keep in mind
A lower average cost does not reduce the loss itself. With more money invested, the same fall causes a bigger loss.
Fees and taxes are not included.
Whether to buy more should depend on the company and your own money plan, not on the average. This calculator only shows numbers; it does not recommend buying.