How does another purchase
change your average share cost?

Read the loss percentage alongside the amount

Average cost is purchase cost per share; return is unrealized profit or loss divided by total invested cost. Adding capital increases that denominator, so a loss percentage can shrink even when the loss amount stays unchanged. A lower average cost does not erase an existing unrealized loss.

The following hypothetical example is in KRW regardless of the currently selected currency. It values 100 shares bought at ₩10,000 at a current price of ₩5,000, then adds 100 shares at that same current price. Fees and taxes are excluded.

The added ₩500,000 becomes holdings worth that same amount immediately after purchase, leaving the original ₩500,000 loss unchanged. The return improves because invested cost rises from ₩1,000,000 to ₩1,500,000. If the purchase price differs from the current price, the new shares also have an unrealized gain or loss.

Equal share counts differ from equal purchase amounts

Buying 100 shares at ₩10,000 and 100 at ₩5,000 gives an average of ₩7,500 because quantities match. Investing ₩1,000,000 at each price instead buys 100 then 200 shares: 300 in total at an average of about ₩6,666.67. More shares were bought at the lower price.

This calculator takes an additional share quantity. To invest an equal amount, first determine the whole shares that amount can buy. Unspent cash is not part of the invested cost shown here.

More shares increase the impact of the next price move

In the example above, a fall from ₩5,000 to ₩4,500 after the purchase leaves 200 shares worth ₩900,000 and an unrealized loss of ₩600,000. That is ₩100,000 less value than immediately after purchase. Keeping only 100 shares would lose another ₩50,000 on the same ₩500 price decline.

Review both the additional capital required and the resulting position size. Average-cost arithmetic summarizes purchase costs; it does not determine why to buy more of an asset or the probability of a price recovery.

The breakeven gain is measured from the current price

When the current price is positive and the position has an unrealized loss, the required gain is (new average cost ÷ current price − 1) × 100. Moving from ₩5,000 to an average cost of ₩7,500 requires a 50% rise. A −33.33% return and a 50% recovery gain use different bases. Actual selling breakeven can differ after fees and taxes.

Explore recovery without added capital · Review portfolio weights after adding a position

Different purchase quantities

New average cost = (existing average × shares held + purchase price × additional shares) ÷ total shares. This differs from a simple average of the two prices.

Precision and currency

Average prices display up to eight decimals and quantities as whole numbers, totals as whole KRW or two-decimal USD, and percentages to two decimals. Calculations use values before display rounding. Switching currency does not convert amounts.

Frequently asked questions