How Stock Splits Work
A stock split divides existing shares into more shares at a proportionally lower price. Your total investment value doesn't change — you simply own more shares at a lower price per share. Companies split their stock to make shares more accessible to retail investors and increase trading liquidity.
The board of directors announces a split ratio (like 2:1 or 4:1) and a record date. On the effective date, your brokerage automatically adjusts your share count and cost basis. You don't need to do anything.
Forward Split vs Reverse Split
Forward splits increase your share count and decrease the price. A 3:1 split turns 100 shares at $300 into 300 shares at $100. Companies do this when their stock price gets high enough to feel “expensive” to individual investors. It's cosmetic — the company's market cap doesn't change.
Reverse splits decrease your share count and increase the price. A 1:10 reverse split turns 1,000 shares at $0.50 into 100 shares at $5.00. Companies use reverse splits to avoid being delisted from exchanges that require minimum share prices (usually $1 on NASDAQ/NYSE). Reverse splits are generally a bearish signal.
How a Stock Split Affects Your Cost Basis
Your cost basis per share adjusts inversely to the split ratio. If you bought 50 shares at $400 each (cost basis: $20,000) and the stock does a 4:1 split, you now own 200 shares with a cost basis of $100 per share. The total cost basis stays $20,000. This matters for calculating capital gains when you sell.
Your brokerage handles this automatically, but always verify. Errors in cost basis after splits are more common than you'd expect, especially if you hold shares across multiple accounts.
Famous Stock Splits: AAPL, TSLA, AMZN
| Company | Date | Ratio | Pre-Split Price | Post-Split Price |
|---|---|---|---|---|
| Apple (AAPL) | Aug 2020 | 4:1 | ~$500 | ~$125 |
| Tesla (TSLA) | Aug 2022 | 3:1 | ~$891 | ~$297 |
| Amazon (AMZN) | Jun 2022 | 20:1 | ~$2,447 | ~$122 |
| Alphabet (GOOGL) | Jul 2022 | 20:1 | ~$2,235 | ~$112 |
| Nvidia (NVDA) | Jun 2024 | 10:1 | ~$1,208 | ~$121 |
| Apple (AAPL) | Jun 2014 | 7:1 | ~$645 | ~$92 |
| Chipotle (CMG) | Jun 2024 | 50:1 | ~$3,283 | ~$66 |
Do Stock Splits Make You Money?
A split itself doesn't create or destroy value. It's like exchanging a $20 bill for two $10 bills. However, research shows stocks tend to outperform in the months following a split announcement. This isn't because of the split itself — it's because companies that split are usually performing well, and the announcement signals management confidence.
The Bank of America found that companies announcing splits returned an average of 25.4% in the 12 months after the announcement, compared to 11.9% for the S&P 500 over the same periods (1980-2023 data). But correlation isn't causation: strong companies split, not the other way around.
What Happens to Options in a Stock Split?
Options contracts adjust automatically. In a 2:1 split, one contract controlling 100 shares at a $200 strike becomes two contracts controlling 100 shares each at a $100 strike. The total notional value stays the same. Non-standard splits (like 3:2) can create odd-lot contracts that are harder to trade.
For splitting investment profits between partners, try our business profit split calculator. To divide equity among co-founders, use the equity split calculator.