Stock split calculator for shares and options
Your stock just split. How many shares do you have now, what did they cost, and what happened to your option? Type the split and your position to see all three.
How it works: a split changes the number of shares, not what you own. New shares = old shares × new ÷ old. Cost per share = old cost ÷ that same factor, so the total cost stays the same. A part share is usually paid to you in cash. Options follow the exchange's rule (the OCC in the US). In a whole-number split like 2-for-1 or 10-for-1, you get that many times more contracts, each strike is divided by the same number, and every contract still covers 100 shares. In any other split, like 3-for-2 or a 1-for-10 reverse split, the number of contracts and the strike stay the same. What changes is the shares one contract delivers: 100 × the factor. That contract is now non-standard. Strikes here are rounded to the cent; the exchange's notice has the exact figure.
Nothing is gained or lost on split day
A 10-for-1 split is like trading a $10 bill for ten $1 bills. You have more pieces, each worth less, and the same total. The same goes for an option. One 1,000-strike contract becomes ten 100-strike contracts. Each still controls 100 shares, and exercising all ten costs the same $100,000 as before. Premium you already collected stays yours. If your option was in the money, it still is. More in what happens when you sold options on a stock about to split.
Reverse splits break the 100-share habit
After a 1-for-10 reverse split, 100 shares become 10. Your old contract now delivers 10 shares, not 100. It gets a new symbol, often with a number on the end, and few people trade it, so prices can be wide. That matters in the wheel strategy: to sell a new covered call after the split you need 100 of the new shares. With 10 you can't sell one. Odd shares are a common surprise. See options after a reverse split and a reverse split left me with odd shares.
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