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Position Size Calculator

Turns capital, risk %, entry, and stop into an exact whole-share position size with dollar risk and R-multiple targets.

Size your trade

Live tool

Stop below entry = long · stop above entry = short. Direction is inferred, never asked.

31shares to buylong
Dollar risk budget
$250.00
Stop distance / share
$8.00
Actual $ risk at stop
$248.00
Position value
$4,030.00
Capital deployed
16.12%
Direction
Long (profit on rise)
R-multiple targets (upward) — 1R = $8.00 per share
1R $138.00
2R $146.00
3R $154.00

Numbers assume your stop order fills exactly at $122.00; a gap through the stop loses more than $248.00.

We floor to whole shares on purpose (conservative, works at every broker). On a fractional-share broker, treat 31.25 shares as an upper bound.

How it works

Position sizing answers the only question you fully control before a trade: how many shares can I buy (or short) so that if my stop is hit, I lose exactly the amount I planned — and no more? You enter your total account capital, the percent of it you're willing to risk on this one trade, your planned entry price, and your stop-loss price. The calculator converts your risk percent into a dollar budget, measures how many dollars per share you lose if the stop fires, and divides one by the other.

Direction is inferred automatically: a stop below the entry means a long trade (buy, profit on a rise), a stop above the entry means a short (sell short, profit on a fall). The share count is always rounded downto a whole share so your realized risk never exceeds your budget, and optional round-trip fees are subtracted from the budget first — fees are a loss you pay even when stopped out. You also get 1R, 2R, and 3R target prices, where one "R" equals your per-share stop distance, plus the R-multiple of your own target price if you provide one.

The formula

  1. Dollar risk budget = capital × (riskPct ÷ 100). Risk % is a percent-number: entering 1 means 1%.
  2. Direction= long if stop < entry; short if stop > entry.
  3. Stop distance = |entry − stop| — dollars lost per share if the stop is hit; identical math long or short.
  4. Shares = floor((dollar risk budget − fees) ÷ stop distance) — rounded down to a whole share so risk never exceeds the budget.
  5. Actual dollar risk = shares × stop distance + fees (always ≤ the budget by construction).
  6. Position value = shares × entry, and capital deployed % = (position value ÷ capital) × 100.
  7. k-R targets = entry + k × stop distance for a long, entry − k × stop distance for a short (k = 1, 2, 3); your target R-multiple = profit distance from entry to target ÷ stop distance.

Worked example

Long setup — NVDA: capital $25,000, risk 1%, entry $130.00, stop $122.00, fees $2.00, target $146.00.

  1. Risk decimal: 1 ÷ 100 = 0.01
  2. Dollar risk budget: $25,000 × 0.01 = $250.00
  3. Direction: stop $122.00 < entry $130.00 → long
  4. Stop distance: |130.00 − 122.00| = $8.00 per share
  5. Raw shares: (250.00 − 2.00) ÷ 8.00 = 248.00 ÷ 8.00 = 31.0
  6. Shares: floor(31.0) = 31 shares
  7. Actual dollar risk: 31 × 8.00 + 2.00 = $250.00
  8. Position value: 31 × 130.00 = $4,030.00
  9. Capital deployed: (4,030.00 ÷ 25,000) × 100 = 16.12%
  10. R-targets: 1R = $138.00 · 2R = $146.00 · 3R = $154.00
  11. Target R-multiple: (146.00 − 130.00) ÷ 8.00 = 2.0R

Short check: capital $10,000, risk 2%, entry $50.00, stop $52.50, fees $0 → budget $200.00; stop above entry → short; stop distance $2.50; 200 ÷ 2.50 = 80 shares sold short; actual risk $200.00; position value $4,000.00 (40.00% of capital); R-targets project downward: 1R = $47.50, 2R = $45.00, 3R = $42.50.

FAQ

How do I calculate position size for a stock trade?

Multiply your account capital by the percent you're willing to risk, then divide by the per-share distance between your entry and stop. Example: $25,000 × 1% = $250 risk; with an $8 stop distance that's 250 ÷ 8 = 31 shares (rounded down).

What is the 1% risk rule?

A common position-sizing convention where a trader risks no more than 1% of account capital on any single trade, so a normal string of losses produces a small, recoverable drawdown. It is a risk-management heuristic, not a guarantee.

Does this calculator work for short positions?

Yes. Place the stop above the entry and it automatically computes a short position, with R-multiple targets projected downward. Note that short selling requires a margin account and losses can exceed the stop if price gaps through it.

What is an R-multiple?

"R" is your initial risk per share — the distance from entry to stop. A 2R target is a price where profit per share equals twice that risk. Traders use R-multiples to compare trades of different sizes on one scale.

Why does the calculator round shares down instead of up?

Rounding up would put more dollars at risk than your budget allows. Flooring to a whole share keeps your actual dollar risk at or below the amount you chose.

What if the calculated position is bigger than my account?

A very tight stop can imply a position value larger than your capital. The calculator flags this, since it would require margin, and also shows the largest whole-share position a cash account could afford.

Continue your analysis

Your entry, stop, capital, and risk % carry forward automatically.

Check this trade's risk/reward ratio →Is your risk % justified by your win rate? →What this risk % means for account survival →Sizing an options trade instead? →