Try these example inputs in the Stock split calculator.
These figures match this guide's worked example. They are illustrative. They stay on this device and never appear in the URL.
A stock split changes how many shares you hold and the price per share. It does not change what the position is worth, and it does not change your total cost. Only the per-share figures move.
Key takeaways
New shares = old shares × (shares received ÷ shares exchanged)
New price = old price × (shares exchanged ÷ shares received)
A 4-for-1 split is 4 shares received and 1 share exchanged. A 1-for-10 reverse split is 1 received and 10 exchanged. The reverse split cuts the share count and raises the price. The totals still match.
You hold 100 shares at $200, with a cost basis of $150 a share. The company splits 4-for-1.
The stock split calculator applies that factor. A split does not, by itself, change market cap either. That point is in what changes market cap.
A reverse split can leave a fraction. 100 shares through a 1-for-3 factor is 33⅓ shares. Brokers often pay cash in lieu of the leftover third of a share, at a price they set around the post-split quote. That cash leaves the share count. Theoretical value of the whole position still matches before the cash-out; after it, you hold fewer shares plus cash. The market can also gap around the split, so conservation is the arithmetic identity, not a promise about the next print.
It keeps your records in line with the new share count: more shares at a lower price, or fewer shares at a higher price, with the same total value and the same total cost.
Brokers usually adjust the basis for you. This page is the arithmetic if you keep your own records. It does not apply a split to a live quote, and it does not handle a cash-and-stock deal. Fractional shares your broker cashes out are shown as cash in lieu when a reverse split leaves a remainder.
Apple shows today's price and share count, with an as-of date. After a split, that page already reflects the new figures. The pre-split price is not still sitting there.
For general education only. Nothing here is investment advice.
Formulas and worked examples are MarketCapLens's. See who checks the numbers.