Guide 4.1
Beginner, 8 min read. Checked with Scalpel 1.12.8 on .
In short
Scalpel has four buy presets, one per key (Shift+1 to Shift+4), and each one sizes the order one of five ways: a fixed share count (Shares), a dollar amount (Notional), or a dollar risk worked out from a stop (Risk (ATR), Risk (Low) or Risk (Cents)). Pick the kind in the order bar's method dropdown or in Settings > Sizing. The line above each buy button shows the dollar size that press would buy at the current ask, so you never fire blind.
How many shares you buy decides how much a bad trade costs you. A fixed share count risks very different money on different stocks; a risk preset keeps the loss at your stop the same on every trade. This guide covers all five kinds, the default ladder, and how to set them up.
Fast small-cap scalping carries a significant risk of loss, and most people who try it lose money. Sizing is your first line of defence: start small, in SIM, and keep the loss per trade to an amount you could take ten times in a row.
Before you start
| Kind | You set | Shares bought | The stop it arms |
|---|---|---|---|
| Shares | A share count | Exactly that many | ATR stop (below) |
| Notional | A dollar clip | Clip / ask, rounded down | ATR stop |
| Risk (ATR) | Dollars of risk | Risk / ATR stop distance, rounded down | 1.5 x ATR under the fill |
| Risk (Low) | Dollars of risk | Risk / (ask - recent low), rounded down | The same distance under the fill |
| Risk (Cents) | Dollars of risk | Risk / Stop (c), rounded down | Exactly Stop (c) under the fill |
Every kind arms a working stop, a wider catastrophe net and a take-profit when it fills (guide 5.1). The difference is whether the stop decides the size (the three risk kinds) or the size is fixed and the stop simply follows (Shares and Notional).
The share count is worked out the instant you press, from the live ask, and always rounded down to whole shares. So a $100 risk preset never puts more than $100 at risk to the stop, before slippage and fees. If the sum comes to zero shares (for example a $1 risk against a $1.50 stop), the order is refused with Order size resolves to zero shares.
A fresh install has all four presets on Shares: 100, 250, 500 and 1,000 shares. Each preset also carries a ready value for the other kinds, so switching the method dropdown gives you a sensible ladder straight away:
| Key | Shares | Notional | Any risk kind |
|---|---|---|---|
| Shift+1 | 100 sh | $2,500 | $25 |
| Shift+2 | 250 sh | $5,000 | $50 |
| Shift+3 | 500 sh | $10,000 | $100 |
| Shift+4 | 1,000 sh | $25,000 | $200 |
The buttons read the way the cheatsheet does: 100 sh, $2500, Risk $25.
The quickest way is the method dropdown 1 on the order bar under the chart. Choosing a kind switches all four presets to it at once and fills in the ladder value above for any preset that has none. Your choice is saved straight away.
Open Settings (Ctrl+,), then Sizing. Each row is one key: the kind on the left, the value in the middle, and the unit after it: shares, $ / clip or $ risk. Values are whole numbers. Click Apply to save, or Cancel to throw the changes away.
Nothing forces the four keys to match. A common mix is two fixed share counts for quick starter clips and two risk buttons for planned entries. The order bar's dropdown then shows the first preset's kind, and each button keeps its own label.
The small line above each buy button is the dollar size that press would put on at the current ask, using exactly the sizing the order will use: $571 over 100 sh at 5.71, $1.9k over Risk $100 with a 30c stop. A dash means there is no ask yet, or the preset sizes to zero. Check it whenever you switch to a stock at a very different price.
Shares is the simplest: press Shift+3 and you buy 500 shares, whatever the price. Your risk is whatever the stop distance happens to be on that stock.
Notional buys a dollar amount: shares = clip / ask, rounded down. $2,500 at a 5.71 ask is 437 shares ($2,495). It keeps the money tied up the same from stock to stock, which helps with buying power, but your risk still changes with the stop.
ATR (average true range, see the glossary) is how far a stock typically moves in one bar. Risk (ATR) puts the stop at 1.5 x the 14-bar ATR on the 1-minute chart and sizes so that stop costs your risk. A jumpy stock gets a wider stop and fewer shares; a quiet one gets a tighter stop and more.
Two limits keep the stop sane:
Worked example: ABCD at 5.71 with a 1-minute ATR of 8c. 1.5 x 8c = 12c, above the 6c floor, so the stop is 12c. A Risk $100 press buys 100 / 0.12 = 833 shares, about $4,756.
The ATR settings live in Settings > Stops (guide 11.3). They also size the stops for Shares and Notional entries.
Risk (Low) puts the stop just under the lowest low of the last 20 one-minute candles, by 0.05% of the price or 1c, whichever is more. The distance from the ask to that level sizes the trade.
Worked example: the 20-bar low is 5.45, so the stop level is 5.44. With the ask at 5.71 the distance is 27c, and Risk $100 buys 100 / 0.27 = 370 shares.
The stop is then armed that same distance under your actual fill. If you fill at the ask it sits right at 5.44; if the order walks up the book, it sits a little higher. If there is no usable low (no candles yet, or the low is not under the ask), Risk (Low) falls back to the ATR stop.
Risk (Cents) puts the stop a fixed number of cents under the fill, 30c by default, and sizes to it: $100 at 30c is 333 shares. It is the most predictable kind and has its own guide: guide 4.2.
For why sizing from the stop matters, read the blog post Sizing by risk.