Discover

Position Sizing Calculator

7 min read

What it is

Industry-standard risk-based position sizing. Pure math, no execution — input account balance + risk per trade % + entry + stop-loss + (optional) take-profit + leverage, get back the exact position size that keeps your loss-on-stop bounded at the risk %. Supports leverage 1x-125x. Optional Kelly mode adds win rate + win/loss ratio inputs for advanced sizing.

How to think about it

Most retail losses come from POSITION SIZE, not strategy quality. A perfect strategy with the wrong size still blows up your account on a normal losing streak. This calculator turns "I think I'll buy 0.1 BTC" into "the math says I can risk exactly 0.08 BTC at this stop-loss to keep my loss at $200 if stopped out". Use it BEFORE every trade.

Step-by-step

  1. Enter account balance + risk per trade %

    Account balance = total capital you are trading with (not just this trade). Risk per trade = % of that balance you accept losing if your stop hits. Standard: 0.5-2%. Aggressive: 3-5%. Above 5% is gambling.

  2. Pick LONG or SHORT direction

    LONG = you profit if price goes up; SHORT = you profit if price goes down. The calculator inverts the stop-loss math accordingly — your stop must be BELOW entry for long, ABOVE entry for short. The page warns you if you flip these.

  3. Enter entry price + stop-loss price

    Entry = where you plan to enter the position. Stop-loss = where you exit at a loss to bound the damage. The DISTANCE between these two prices determines your position size — wider stop = smaller size to keep risk at the same dollar amount.

  4. Enter take-profit (optional) for R:R math

    Optional. If provided, the calculator returns the Risk/Reward ratio (e.g., R:R = 2.5 means you risk $1 to make $2.50). R:R ≥ 2 is the conventional retail floor; R:R < 1 means you risk more than you stand to gain — usually a sign to skip the trade.

  5. Adjust leverage if using futures

    Leverage slider 1x to 125x. 1x = spot (no leverage). Higher leverage = smaller required margin but proportionally larger liquidation risk. Spot traders leave at 1x. Futures traders at 3x-10x for swing trades, 25x+ only for tightly-stopped intraday plays.

  6. Toggle Kelly mode for advanced sizing

    Show Kelly checkbox reveals 2 extra inputs: win rate (e.g., 0.55 = 55%) and average win/loss ratio (e.g., 2 = your average winner is 2× your average loser). Kelly returns the mathematically optimal % to risk per trade given those stats. Quarter Kelly (output × 0.25) is the practical retail floor — Full Kelly produces wild drawdowns.

  7. Read the calculated position size + auto-update

    Result panel shows: position size in base units, notional value in USD, leverage applied, R:R ratio (if TP provided), liquidation price (if leveraged). Inputs are auto-recalculated 300ms after you stop typing. No need to click Calculate.

Tips & pitfalls

  • Risk per trade is the most-important number on this page. 1% per trade means you can lose 20 trades in a row and still have ~82% of your account. 5% per trade and 20 losers leaves you with ~36%. Position-size discipline outlives strategy edge.
  • Wide stop = small size; tight stop = large size. The dollar-loss-on-stop stays constant. This is the entire point of risk-based sizing — emotion ("I want to buy 1 BTC") loses to math ("0.08 BTC is what 1% risk at this stop allows").
  • R:R math is informational. The calculator does NOT enforce a minimum R:R — many profitable strategies have R:R < 2 with very high win rates. Just be honest: a 65% win rate at R:R 1.2 beats a 30% win rate at R:R 3.
  • Leverage does NOT increase profit potential per dollar risked — it only changes the MARGIN required. A 10x leveraged 1% risk position has the same dollar P&L as a 1x leveraged 1% risk position. Leverage is a capital-efficiency tool, not a return multiplier.
  • Liquidation price is your hard floor on leveraged positions. If your stop-loss is BEYOND liquidation, the exchange closes you before your stop fires — you eat the maintenance-margin loss, not the intended stop-loss loss. The calculator warns when this happens.
  • Kelly Criterion in raw form is too aggressive for retail. Full Kelly assumes infinite trials and zero variance in your win-rate estimate. Use Quarter Kelly (multiply output by 0.25) as the practical retail floor.
  • The calculator does NOT place trades. Use the calculated size as the input to your actual order on CEX Trading / DEX Swap / Futures / Smart Trade. This is a tool, not a router.
  • Audit yourself weekly: take last 10 trades, check whether your actual position sizes match what THIS calculator would have suggested. Discipline gaps show up here long before they hit your P&L.