Stock Water Buy
Stock Water Buy — runs in your browser. Inputs are not stored.
Stock average-down calculator (for reference)
Enter values, then press Calculate.
Fees and taxes not included.
How to use
- Enter shares held and average cost (KRW). The default sample is 100 shares at 50,000 KRW.
- In current price (KRW), enter the price you would buy at now. The default is 40,000 KRW.
- In target average cost (KRW), enter the average you want after averaging down. The default is 45,000 KRW.
- Averaging down is valid only when current price < target average < holding average. Outside that, a notice appears.
- Press Calculate to see extra shares needed (rounded up), extra buy amount, and total shares and amount after averaging down. Fees and tax are omitted.
Key concepts
Averaging down (mul-tagi) means buying more at a lower price to reduce average cost. Extra shares = shares held × (average − target) ÷ (target − current price). This tool shows that value rounded up to a whole share, and extra buy amount = rounded shares × current price. Buying at a price already above your average is closer to averaging up (bul-tagi), not averaging down.
The stock average-cost calculator adds past buys to answer “what is my average now.” This screen works the other way: “how many more shares do I need now to hit a target average.” Results are for reference and are not investment advice. Fees, taxes, and tick sizes are omitted. Averaging down is extra buying, not a sale that locks in a loss, so check cash and diversification limits first. The number is only a quantity reference for a target average, not a buy recommendation.
Example
100 shares, average 50,000, current 40,000, target 45,000 → extra shares = 100×(50000−45000)÷(45000−40000)=100. Extra buy 4 million KRW, total after 200 shares, total amount 9 million KRW. A target closer to the average, such as 48,000, needs more extra shares. Fractional shares are rounded up. If the target is very close to the average, required shares jump—match cash to the extra-buy field. If current < target < average does not hold, you get a notice instead of a calculation.
Related: Stock average-cost calculator · Percentage calculator
Frequently asked questions
How does the averaging-down calculator differ from the average-cost calculator?
Average cost sums shares you already bought. This tool reverse-calculates how many more shares to buy now to hit a target average. Use the average-cost calculator to combine past buys.
What if the current price is above the target?
It does not calculate. Current must be below target, and target below your holding average.
Why are extra shares rounded up?
Shares are usually whole units, so it rounds up to the minimum whole shares needed. The actual average may come out a little below the target.
Are fees and transaction tax included?
No. Brokerage fees and taxes are separate.
Does fractional overseas-share trading work?
This version uses rounded-up whole shares. Follow the broker’s rules for fractional trades.
Are shares held saved?
No. Reverse calculation runs only in the browser and is not linked to an account.
Last reviewed: 2026-09-04