# position-sizer

Calculates share quantities for long stock trades using risk, stop distance, and portfolio limits. Useful for comparing Fixed Fractional, ATR, and Kelly sizing.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 403 installs · ★ 142
- Author: Wind-Alice
- License: not stated · policy=link-only · description only; the file stays with the author
- Source: https://github.com/Wind-Alice/AliceMarket/tree/HEAD/skills/position-sizer/SKILL.md
- Updated: 2026-10-15
- HTML: https://affpapa.org/en/nevibecode/skills/wind-alice-position-sizer

## What it does

The skill gathers trade inputs and runs a Python script. Fixed Fractional uses a chosen share of account equity at risk; ATR sizing adjusts the stop distance for volatility, while Kelly uses win-rate and win/loss figures. If no method is selected, the agent compares several risk settings and ATR multipliers.

You can set caps for position size and sector exposure, along with current sector exposure. The tightest applicable cap determines the final share count. The script rounds down to whole shares and writes JSON and Markdown reports to `reports/`. It requires Python 3.9+ and the Python standard library; no API keys are needed.

For a share calculation, provide an entry price and stop, or an ATR value, depending on the method. Kelly also needs the win rate, average win, and average loss. Without entry and stop prices, Kelly can still estimate a risk budget, but not the share count.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add Wind-Alice/AliceMarket --skill position-sizer -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/position-sizer/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/position-sizer/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add Wind-Alice/AliceMarket --skill position-sizer -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/position-sizer/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add Wind-Alice/AliceMarket --skill position-sizer -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/position-sizer/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install Wind-Alice/AliceMarket position-sizer
```

2. **Manually: put the files in place**
- File: `.github/skills/position-sizer/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add Wind-Alice/AliceMarket --skill position-sizer -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/Wind-Alice/AliceMarket --path skills/position-sizer
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/position-sizer/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add Wind-Alice/AliceMarket --skill position-sizer -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/Wind-Alice/AliceMarket/tree/HEAD/skills/position-sizer/SKILL.md

## When to use it
- calculate shares for a defined account risk
- set a volatility-based stop distance with ATR
- estimate risk allocation from trade results
- check a trade against position and sector caps
- compare position sizes across risk settings

## Example prompts
- Calculate shares for a 25000 account with an entry at 80, a stop at 76, and 1% risk.
- Compare fixed-risk and ATR sizing for these trade inputs.
- Check how a sector cap changes the position with current exposure at 18%.

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## Other versions with the same name
- [position-sizer · tradermonty](https://affpapa.org/en/nevibecode/skills/position-sizer.md) — 3800 installs

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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md