The position-sizing framework: 1-2-5 rule. Allocate no more than 1% of portfolio to any single low-conviction speculative options trade, 2% to high-conviction directional bets, 5% to defined-risk income strategies on quality underlyings (cash-secured puts, covered calls on large-caps). Maximum total options exposure: 25% of portfolio. Maximum single underlying exposure: 10% of portfolio across all positions. These numbers seem conservative but match the empirical survival rate of retail options traders.
This page gates Level 3 — Exposure, and is read first at Level 1
Sizing is the last gate before the advanced tier, because Level 3 is where a sizing error stops being expensive and starts being terminal. Before you trade any Level 3 structure, you should be able to tick every item on this list from this page alone:
- Max loss per contract. Spread width × the contract multiplier, minus the credit: a £5-wide spread risks £500 per contract before the credit and £380 after a £1.20 credit — never the per-share figure.
- Collateral for a cash-secured put. Strike × the contract multiplier: £2,500 funds exactly one contract at a £25 strike, and a £175 strike ties up £17,500 however attractive the premium looks.
- The 100× error class. Reading a per-share width or premium as the per-contract figure understates the commitment by the multiplier. Earlier versions of this page contained errors of exactly that class, since corrected — which is the strongest argument for re-doing the multiplication yourself before every trade.
- Margin vs cash account. Selling options requires margin; adverse moves can force cash deposits mid-trade, and stop-loss orders do not protect against overnight gaps.
- The framework. The 1-2-5 rule per trade, a 25% ceiling on total options exposure, 10% per underlying, and a 25% cash reserve.
One sentence carries the whole of the advanced tier: undefined-risk structures are sized from buying power and tail exposure — what a gap does to your margin requirement — not from expected return.
You are ready for Level 3 when… every position's maximum loss, collateral and margin requirement is a pound figure you wrote down before entry, and your book would survive a 20% overnight gap. Then open Level 3 — Exposure.
Why position-sizing is the #1 risk factor
The mathematics: even a 70% win rate strategy can blow up if losses are 4× the average win.
| Win rate | Win/loss ratio | Long-term outcome |
|---|---|---|
| 70% | 1:1 | Positive expectancy |
| 70% | 1:4 (loss is 4× win) | NEGATIVE expectancy |
| 50% | 2:1 (win is 2× loss) | Positive expectancy |
| 30% | 5:1 | Positive expectancy |
Position-sizing controls the win-to-loss size ratio. If you let losers run to -100% (-£500 on a £500 premium) and cap winners at +50% (+£250 on a £500 long position), even 60% win rate is losing.
The 1-2-5 rule for UK retail
1% — speculative directional bets
Out-of-the-money long calls/puts, lottery-ticket trades on individual stock moves, biotech/earnings plays. Maximum 1% of portfolio. For a £50,000 portfolio, that's £500 per trade.
2% — high-conviction directional bets
In-the-money calls/puts with clear thesis, hedges for existing positions, defined-risk spreads on high-conviction ideas. Maximum 2% of portfolio. For a £50,000 portfolio, that's £1,000 per trade.
5% — defined-risk income strategies on quality underlyings
Cash-secured puts on large-caps you're happy to own and covered calls on existing positions. Maximum 5% of portfolio in collateral. For a £50,000 portfolio, that's £2,500 of cash collateral per trade. (Iron condors and other spreads are defined-risk trades and sit in the 2% band above, sized by maximum loss. Undefined-risk structures sit outside this ladder altogether: the Level 3 pages size them by initial margin, no more than 5% of net liquidation value, with a 20% gap loss no more than 10%.)
Be precise about what "5%" buys on a short put. The collateral is the strike times the contract size: 100 shares on a US contract, 1,000 on a traditional ICE UK series — so £2,500 funds exactly one US contract at a £25 strike, and no ICE contract on most FTSE 100 shares. A single put on a £175 share needs £17,500 of collateral (35% of the portfolio) and risks £17,500 less the premium if the shares go to zero. At £50,000 of capital that trade is off-limits however attractive the premium looks, and the defined-risk substitute is a put spread, where the width rather than the strike sets the risk.
Portfolio-level limits
- Maximum total options exposure: 25% of portfolio. If your portfolio is £50,000, max £12,500 deployed across all options positions at any time.
- Maximum single underlying: 10% of portfolio. Don't have £8,000 of AAPL exposure across calls, puts, and shares.
- Maximum correlated exposure: 15% of portfolio. Tech stocks correlate with each other — limit total tech-options exposure regardless of individual position sizes.
- Maximum cash collateral: Sufficient for all open cash-secured puts AT THE STRIKE. If you have 5 cash-secured puts each requiring £5,000 of collateral, you need £25,000 of cash sitting in the broker.
Worked example — sizing a portfolio
£50,000 portfolio building options exposure
Every figure below is capital actually committed: collateral for short puts, net risk for spreads, premium paid for long options. One US-listed contract covers 100 shares and a traditional ICE UK contract 1,000, so multiply every per-share price by the contract's own size before comparing it to the portfolio. (The figures below use the 100-share US contract; US-listed options are USD-denominated and pounds are used throughout for comparability.)
| Position | Allocation | Capital committed (maximum loss) |
|---|---|---|
| Cash-secured put, 1 contract, £25 strike, £0.70 premium | 5% | £2,500 collateral (max loss £2,430) |
| Bull put spread, 2 contracts, £5 wide, £1.20 credit | 1.5% | £760 = 2 × (£5.00 − £1.20) × 100 |
| Covered call, 1 contract, against 100 shares already held | — | No new capital; £150 premium received |
| Long FTSE 100 put for hedging (£10 per index point) | 2% | £1,000 premium paid |
| Speculative single-stock earnings call | 1% | £500 premium paid |
| Long-dated call (high-conviction directional) | 2% | £1,000 premium paid |
| Total options exposure | 11.5% | £5,760 |
Notice what is missing. There is no cash-secured put on a £175 or £300 share, because one contract at a £175 strike would tie up £17,500 of collateral — 35% of this portfolio and seven times the 5% cap. At £50,000 of capital, cash-secured puts are only available to you on low-priced underlyings; on expensive ones you use a put spread instead, where risk is set by the width, not the strike.
This is a sustainable level: £5,760 is 11.5% of the portfolio, comfortably inside the 25% ceiling. If the four largest positions all went to maximum loss in the same month — £2,430 + £1,000 + £1,000 + £760 = £5,190 — that is 10.4% of capital. Painful, recoverable, and nowhere near account-ending.
Now consider the alternative: a single £20,000 long call (40% of portfolio) on a 5-week earnings bet. One bad earnings = £20,000 loss = 40% of portfolio gone. Catastrophic.
The maximum-loss rule
For every position, before opening:
- Calculate maximum loss in pounds. For long calls/puts: the premium paid. For sold puts: strike × contract size minus premium received. For spreads: width of spread × contract size minus credit. The contract size is 100 shares on a US contract, 1,000 on a traditional ICE UK series and £10 per point on the FTSE 100.
- Compare to portfolio. Is the maximum loss above the 1-2-5 band for the structure (1% speculative, 2% directional and spreads, 5% collateral for a cash-secured put)? Don't open.
- Set a stop. If you'll close at -50% of premium, what's the actual GBP loss at that point? Make sure it's tolerable.
The losing streak survival framework
Even with positive expectancy, losing streaks happen. A 5-trade losing streak at -100% each on 5% positions = 25% portfolio drawdown. Survivable. The same streak on 20% positions = portfolio destroyed.
Mathematical fact: at 60% win rate, a 5-loss streak is ~1% probability — happens every 100 trades. Plan for it.
Drawdown rule: if your options portfolio is down 20% from peak, reduce all position sizes by 50% for the next 10 trades. Re-evaluate after.
The cash reserve
Always hold at least 25% of your total portfolio in cash, even if you're heavily options-active. The cash serves three functions:
- Collateral for unexpected assignments on cash-secured puts.
- Margin for sold positions (if a put position moves against you, additional margin may be required).
- Opportunity capital — when markets crash and IV spikes, premium-selling becomes lucrative. You need cash to deploy.
Common position-sizing mistakes
- Doubling down on losers. Adding to a losing position to "average down" multiplies your loss when wrong. Don't.
- Over-leveraging via spreads. Width is quoted per share, but one US contract covers 100 shares and a traditional ICE UK contract 1,000. A $5-wide US spread risks $500 per contract before the credit and $380 after a $1.20 credit — so 10 contracts is $3,800 of real risk, not $380; a 50p-wide ICE spread risks £500 per contract. A 100-point-wide FTSE 100 spread risks up to £1,000 per contract at £10 a point, and £10,000 across ten. Multiply the width by the contract size before you decide on size.
- Ignoring overnight gaps. Stop-loss orders don't work overnight. A 20% gap-down on Friday morning can blow through any stop.
- Forgetting margin calls. Selling options requires margin. Adverse moves can force you to deposit cash mid-trade.
Sources and methodology
The 1-2-5 framework reflects standard retail options risk management. Win-rate / win-loss ratio mathematics are well-established. Every pound figure on this page uses the standard contract multiplier of 100 shares per US-listed equity option — see the OCC's Characteristics and Risks of Standardized Options — and £10 per index point for ICE FTSE 100 index options. For personalised investment advice, an FCA-authorised IFA is required (UK Tax Drag is educational only). See the tax adviser editorial recommendation. The methodology page documents sources.
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