Account size & margin
How the allocation bar, buying power and margin math work — including the (width − premium) × 100 rule and call/put netting.
As soon as you add strategies, the allocation bar above the catalog turns into a live buying-power gauge for your selection.
Reading the bar
- The right-hand readout is $ deployed / your buying power · percent used —
e.g.
$48,500 deployed / $100,000 · 49%. - The bar itself shows margin share by strategy family (MEIC, METF, Ratio, …): a family using 20% of your buying power fills 20% of the track.
- The dollar figure next to the readout is editable — set it to your real account size and the gauge rescales. If the selection exceeds it, the bar tells you by how much.
Two scopes to keep apart: the account size drives only this gauge and the Portfolio Builder's dollar figures. The catalog's performance metrics stay normalized to the standard $100k account per contract, so rows remain comparable no matter what you type here.
The margin math
For a defined-risk credit spread, the maximum loss — and therefore the margin a broker holds — is:
Max margin per contract = (width − premium) × 100
A 100-wide spread collecting $3.00 risks (100 − 3) × 100 = $9,700 per contract. That's also why width is the dominant lever on capital use.
Call/put netting: call spreads and put spreads on the same expiry can't both lose to the full extent — the underlying finishes on one side. So each call/put pair is margined at the larger side only; the paired side rides free. An iron condor therefore consumes the margin of one side, not two. Ratio structures are charged their complex's max loss.
The Workbench applies this netting across your whole selection, which is why adding an opposite-side strategy can raise your deployed margin by less than its face amount — sometimes by nothing at all.
Practical guidance
- Filter with your realistic buying power in mind: a shortlist that deploys 150% of your account is a fantasy list.
- Leave headroom. 100% deployed means zero slack for adjustments, assignment quirks, or simply being wrong about margin at the open.
- Contract scaling happens in the Portfolio Builder — the Browser counts every selection at one contract.