Stock Average Calculator – Average Down

Find Your Average Cost per Share or Plan an Average Down

Calculation mode

Your purchases — up to 20 (a new row appears as you fill the last one)

Shares (1)

Price per share (1)

Fees (1)

Commission or fee paid on this purchase — optional, counted in your total cost.

Shares (2)

Price per share (2)

Fees (2)

Current share price

Optional — used to show your position's current value and unrealized gain or loss.

Calculate automaticallyIf enabled, the result will update automatically when you change any value.

Your Position

Position summary

Total shares

Total cost

Average price per share

Current value

Unrealized gain or loss

Position return

Purchase breakdown

Shares to buy

Cash needed (excluding fees)

How averaging down works

Stock Average Formula

Formula

\[ \text{Average price per share} = \frac{\sum_{i=1}^{n} \left( s_i \cdot p_i + f_i \right)}{\sum_{i=1}^{n} s_i} \qquad \text{Shares to buy to average down:} \quad m = \frac{S \cdot (A - T)}{T - P} \]

Where:

$s_i$ — shares bought in purchase $i$
$p_i$ — price per share paid in purchase $i$
$f_i$ — commission or fee paid on purchase $i$
$S$ — number of shares you currently hold
$A$ — your current average cost per share
$P$ — current share price (the price at which you would buy more)
$T$ — target average price
$m$ — shares you need to buy

The first formula is total invested money divided by total shares owned — the weighted average of all your purchase prices, fees included. The second formula answers the reverse question: given a position and a lower price, how many additional shares pull your average down to a chosen target.

Stock Average – Calculation Example

Example 1 — average cost: you buy 50 shares at $30 and later 100 shares at $24, no fees, and the stock now trades at $22.

\[ \text{Total cost} = 50 \times 30 + 100 \times 24 = 1{,}500 + 2{,}400 = 3{,}900 \]
\[ \text{Average price} = \frac{3{,}900}{50 + 100} = \frac{3{,}900}{150} = 26 \]
\[ \text{Current value} = 150 \times 22 = 3{,}300, \quad \text{unrealized loss} = 3{,}300 - 3{,}900 = -600 \; \left( -15.38\% \right) \]

Result: 150 shares, $3,900 invested, an average cost of $26 per share, currently worth $3,300 — an unrealized loss of $600, or −15.38%.

Example 2 — average down: you hold 100 shares with an average cost of $25, the price has fallen to $15, and you want an average of $20.

\[ m = \frac{100 \times (25 - 20)}{20 - 15} = \frac{100 \times 5}{5} = 100 \text{ shares}, \quad \text{cash needed} = 100 \times 15 = 1{,}500 \]

Result: buy 100 more shares at $15 for about $1,500. Your position becomes 200 shares costing $4,000 — an average of exactly $20 per share.

How to use the calculator

Choose the Calculation mode: Average cost of my purchases or Average down — reach a target average price.
In average-cost mode, enter each purchase's Shares, Price per share and optional Fees. Fill the last visible row and a new one appears — up to 20 purchases.
Optionally enter the Current share price to see your position's value and unrealized gain or loss; leave it blank to skip that part.
Read the Position summary: total shares, total cost, average price per share and, if a current price was given, current value, unrealized gain/loss and position return.
Check the Purchase breakdown table to see each purchase's cost and how the running average moved after each buy.
In average-down mode, enter Shares you hold, Your average cost per share, Current share price and Target average price. The result shows Shares to buy and the Cash needed to reach that target.
Make sure the target average is above the current price but below your current average — that is the only zone averaging down can reach, and the calculator warns you otherwise.

What “average price” and “averaging down” mean

Your average price per share (also called cost basis, average cost or break-even price) is the total amount of money you invested divided by the number of shares you bought across all purchases. It matters for two reasons. First, it is the price at which selling the whole position returns exactly what you paid — your break-even point. Second, when you eventually sell, the taxable gain or loss is measured against this average, not against any single purchase price.

Most brokers report your average cost automatically, but their figures can be confusing after partial sales, transfers between accounts, dividend reinvestments or fee-charged purchases. Recomputing it yourself — including commissions — shows what the position truly cost you, and whether your paper profit matches reality.

Averaging down means buying more shares after the price falls, which lowers your average cost. In the example above, buying at $24 pulled the average from $30 down to $26, so the stock only needs to recover to $26 for you to break even instead of $30. In the planning mode, the calculator tells you precisely how many additional shares at today's price achieve your chosen target average. The closer the target is to the current price, the more shares — and cash — it takes, which is exactly what the second formula captures.

Lowering your break-even sounds attractive, but averaging down is a two-edged tactic. The unrealized loss in dollars grows as the position grows, and you are concentrating more of your portfolio in an asset that is falling. It works best as a deliberate, pre-planned move — not as an emotional response to seeing red on the screen.

Assumptions, limitations and practical tips

Fees count. Commissions raise your true average cost, so include them in the Fees fields. In average-down mode, add any buying fee on top of the cash figure shown.
Fractional shares. The average-down answer is often not a whole number. Brokers that support fractional shares, and crypto, can use it exactly; otherwise round up to land at or below your target.
Reachable targets only. Buying at price $P$ can pull your average toward $P$ but never to or below it. A target at or below the current price is mathematically unreachable; a target at or above your current average requires no purchase.
Same tax lot rules may differ. Some brokers and tax systems use lot-based accounting (specific shares, FIFO) rather than simple averaging. The number here is your economic average, not tax advice — check which method applies to you before selling.
Sale proceeds are not included. If you sold part of the position, enter only the purchases behind the shares you still hold.
Risk check before averaging down. Ask whether you would buy this asset at today's price if you didn't already own it. Also track how big the position is becoming relative to your total portfolio with the Net Worth calculator, and consider how dividends change your effective return with the Dividend calculator.
If you trade derivatives rather than shares, the Options Profit calculator handles position math for options, and the Compound Interest calculator shows what the same cash could earn elsewhere.

Frequently Asked Questions

How do I calculate my stock average price in Excel or Google Sheets?

List each purchase's shares in column A and total cost (shares × price + fees) in column B, then divide the sums: =SUM(B:B)/SUM(A:A). If you only have prices without fees, use =SUMPRODUCT(A:A,price_column)/SUM(A:A). Update the ranges as you add purchases, or convert the data to a Table so the formulas expand automatically.

What happens to my average cost if I sell some of my shares?

Under simple average-cost accounting, selling shares does not change your average price — you keep the same cost basis on whatever remains. Under lot-based methods (FIFO, specific identification), you sell particular lots, so your remaining average can jump up or down depending on which lots you chose. Check which method your broker and tax authority use before relying on the average shown here.

Why can't I ever average down to the current price?

Every share you buy at price $P$ pulls the blended average toward $P$, but the old, more expensive shares never disappear — so the average always stays above $P$. As your target approaches $P$, the required purchase grows without limit, because $m = S(A-T)/(T-P)$ divides by that shrinking gap. That is why a realistic target sits closer to your current average than to the market price.

Is averaging down the same as dollar-cost averaging?

No. Dollar-cost averaging means investing a fixed amount on a regular schedule regardless of price direction — it is a passive, planned strategy. Averaging down means deliberately adding to a position specifically because it has fallen, increasing your exposure to a loser. The math is the same weighted average, but dollar-cost averaging spreads risk across time while averaging down concentrates it in one asset.

Should dividend reinvestments be counted as purchases?

Yes. Each reinvested dividend buys fractional shares at that day's price, so it is a real purchase that belongs in your cost basis. Brokers usually track this for you, but if you are computing the average manually, add these buys as extra rows. Note that reinvested dividends are typically treated as taxable income in the year received, which again widens the gap between economic and tax cost basis.

Does this calculator work for crypto like Bitcoin or Ethereum?

Yes — enter your coin quantities instead of share counts and the price per coin for each purchase. Crypto trades fractionally, so the exact fractional answer in average-down mode is usable as-is, unlike whole-share markets. The same caveats apply: include trading and network fees, and remember exchanges may use different accounting methods for reporting your gains.

What is the biggest mistake people make when averaging down?

Committing too much capital too fast. Some investors double their position to shave a few dollars off the average, then have no cash left if the price falls further — the classic martingale trap. A disciplined approach is to set a maximum position size as a share of your portfolio beforehand, average down only in planned steps with a reasoned investment case, and never buy more simply to feel better about a red number.