How to use this calculator
- Enter the current share price and days to expiration.
- Enter the body strike (usually at the money) and the premium you collect on the put and the call sold there.
- Enter the long call — its strike (above the body) and the premium you pay.
- Set the number of contracts — each multiplies the credit and the risk by × 100.
- Read the result: net credit, whether there is upside risk, the downside breakeven, max loss and return on capital.
What it tells you: whether the fat at-the-money credit clears the call width to remove upside risk, and what the at-the-money cash-secured-put downside costs.
How this calculator works
A Big Lizard is the Jade Lizard taken to its at-the-money extreme. Instead of a separate out-of-the-money put and call, you sell both at the same body strike — a short straddle — and buy one higher call to cap the call side. The net credit is the two premiums you collect minus the one you pay, and an at-the-money straddle pays a lot, so the credit is large.
That fat credit is what makes the no-upside-risk rule easy to satisfy: as long as the credit is at least the call-spread width (long call minus body strike), a rally can only cost the spread's width, which the credit already paid for. Above the long call you still keep credit minus width. The trade-off is the profit shape: because the put and call sit together, you keep the full credit only at the body strike, and you give some back as the stock drifts either way.
The real risk is the downside, and it is bigger than a Jade Lizard's because the short put is at the money, not out of it. It behaves like an at-the-money cash-secured put: below the breakeven (body strike minus credit) you lose, down to that breakeven times 100 if the stock collapses. Capital and return on capital are shown on that cash-secured-put basis (body strike × 100).
Worked example
A fixed, hypothetical illustration — not live market data.
A stock trades at $100. With 45 days left you sell the 100 put for $3.00 and the 100 call for $3.20 (a $6.20 at-the-money straddle), and buy the 105 call for $1.00 — a $5.20 net credit against a $5.00-wide call spread.
- Net credit / max profit: $5.20 × 100 = $520, kept in full only at $100.
- No upside risk: credit $5.20 ≥ width $5.00, so even above $105 you keep $20.
- Downside breakeven: $100 − $5.20 = $94.80 (also the cost basis if assigned).
- Max loss: ($100 − $5.20) × 100 = $9,480 if the stock goes to zero.
- Capital / return: $100 × 100 = $10,000 secured; $520 ÷ $10,000 = 5.2%, about 42% annualized.
Edge cases this calculator handles
- Profit only at the body. Unlike a Jade Lizard's wide shelf, the full credit is kept at a single strike, so the calculator shows the peak and the floor honestly rather than implying a forgiving range.
- A credit that doesn't cover the call width. Rare for an ATM body, but if your call spread is very wide the trade carries upside risk again — the calculator flags it and shows the upside loss and breakeven.
- The downside is open, and larger than a Jade Lizard's. The ATM short put has no long put behind it, so the max-loss figure is the at-the-money cash-secured-put loss to zero.
- Zero days to expiration. Annualized return shows "N/A" rather than dividing by zero.
Common mistakes
- Forgetting the downside is an ATM naked put. The "no upside risk" headline hides a bigger downside than the Jade Lizard — only trade it on a stock you would own at the money, and secure the cash.
- Expecting a wide profit range. The body is a straddle; the full credit lives at one strike. If you want a forgiving range, use a Jade Lizard or an iron condor instead.
- Selling the body when volatility is low. The whole structure leans on a fat at-the-money credit; in cheap volatility it barely covers the call width and the reward thins out.
- Letting a tested put ride. If the stock breaks down, manage the short put like any cash-secured put — roll or take assignment — rather than freezing.
Frequently asked questions
What is a Big Lizard?
A Big Lizard is a Jade Lizard with the short put and short call at the same at-the-money strike — a short straddle, capped on the call side by a long call. You sell the ATM put, sell the ATM call and buy a higher call, all for a net credit. As with a Jade Lizard, when that credit is at least the width of the call spread there is no upside risk; the only risk is the downside, a cash-secured put at the body strike.
How is a Big Lizard different from a Jade Lizard?
Both bundle a short put, a short call and a long call for a credit with no upside risk. In a Jade Lizard the put and short call are out of the money, so the trade keeps the full credit across a range. In a Big Lizard they sit together at the money, so it collects a much larger credit but keeps the full amount only if the stock pins the body strike at expiration. The Big Lizard trades a wider profit zone for a fatter, more demanding credit.
Does a Big Lizard really have no upside risk?
Yes, when the net credit is at least the call-spread width. A rally caps the call spread loss at its width, which the at-the-money credit easily covers, so above the long call you still keep credit minus width. If the credit is smaller than the width — unusual for an ATM body, but possible with a wide call spread — there is a capped upside loss instead, which the calculator flags.
What is the risk on a Big Lizard?
The downside, and it is larger than a Jade Lizard's because the short put is at the money rather than out of the money. Below the breakeven (body strike minus credit) you lose like a cash-secured put, down to that breakeven times 100 per contract if the stock falls to zero. Only run it on a stock you would be content to own at the body strike, and secure the cash.
When should you use a Big Lizard?
When you are neutral on a stock you would own at the money and implied volatility is high enough that the at-the-money straddle pays a credit comfortably above the call width. It suits a name you expect to pin a level into expiration. Skip it if you have a directional lean — the symmetric body wants the stock to sit still — or if you would not want to own the shares at the current price.
Related tools and guides
Spread the body out for a wider range with the Jade Lizard Calculator, or cap the downside too with the Iron Butterfly Calculator.
Its downside is an at-the-money cash-secured put — size it with the Cash-Secured Put Calculator, check premium is rich first with the IV Rank Calculator, and see the setup conventions in strategy setups.
Educational tool only. Nothing here is financial advice. A Big Lizard removes upside risk but its downside is an at-the-money cash-secured put: a sharp drop can cost far more than the credit, down to the breakeven times 100 if the stock collapses. Size and secure the put accordingly.