Understanding your stock split results
The table below contrasts forward and reverse splits, using the mechanics this calculator applies.
| Split type | Example ratio | Effect on share count | Effect on share price | Effect on position value |
|---|---|---|---|---|
| Forward split | 4-for-1 | Multiplied by 4 | Divided by 4 | Unchanged |
| Forward split | 2-for-1 | Multiplied by 2 | Divided by 2 | Unchanged |
| Reverse split | 1-for-10 | Divided by 10 | Multiplied by 10 | Unchanged |
- Real-world splits can produce fractional shares (for example, holding 25 shares in a 3-for-2 split); brokers typically pay cash in lieu of fractional shares, which this calculator does not model.
- A split changes only the denomination of ownership; it does not change the company's market capitalization, earnings, or any shareholder's percentage ownership.
- Market prices after a split are set by trading, so the actual post-split price can drift from the exact arithmetic adjustment once the market reopens.
What is a stock split?
A stock split is a corporate action in which a company divides each existing share into multiple shares, increasing the share count while reducing the price per share by the same proportion. The U.S. Securities and Exchange Commission's Investor.gov explains that a split increases the number of shares outstanding but does not change the total dollar value of the company or of any individual shareholder's stake.
In a forward split such as 4-for-1, each shareholder receives four new shares for every one previously held, and the share price is divided by four. In a reverse split such as 1-for-10, every ten shares are consolidated into one, and the price per share is multiplied by ten. Companies typically use forward splits to bring a high share price into a more accessible trading range, and reverse splits to raise a low share price, sometimes to meet exchange listing requirements.
Because a split is purely a change in denomination, financial metrics quoted per share — earnings per share, dividends per share, and historical price charts — are retroactively adjusted by data providers so that per-share comparisons across the split date remain valid.
How to use this stock split calculator
- Enter the number of shares you own before the split.
- Enter the share price before the split.
- Enter the split ratio: the number of new shares in the first field and the number of old shares they replace in the second. A 4-for-1 split is 4 new for 1 old; a 1-for-10 reverse split is 1 new for 10 old.
- Read the new share count, the adjusted price per share, and the total position value — which is the same before and after the split.
The formula behind a stock split
The split ratio is the number of new shares divided by the number of old shares they replace. The share count is multiplied by this ratio, and the share price is divided by it, so the product of shares and price — the position value — is unchanged.
For example, in a 4-for-1 split, 100 shares at $150 become 400 shares at $37.50. The position value is $15,000 in both cases: 100 × $150 = 400 × $37.50 = $15,000.
Common mistakes
- Believing a stock split makes a position more valuable — the number of shares rises but the price falls proportionally, leaving the total value unchanged.
- Reversing the ratio fields — a 4-for-1 forward split means 4 new shares per 1 old share; entering 1 new for 4 old would instead model a reverse split.
- Comparing pre-split and post-split share prices or EPS without adjustment, which makes historical charts and per-share metrics look discontinuous.
- Assuming a reverse split signals the same thing as a forward split — reverse splits are often used to lift a low share price, sometimes to maintain exchange listing standards, which is a different context than a high-flying stock splitting to improve accessibility.
Questions fréquentes
Does a stock split change the value of my investment?
No. A stock split changes the number of shares you own and the price per share in exact proportion, so the total value of the position is the same immediately before and after the split. In a 4-for-1 split, 100 shares at $150 ($15,000) become 400 shares at $37.50 — still $15,000.
What is a 4-for-1 stock split?
A 4-for-1 stock split gives shareholders four new shares for every one share they previously owned, while the share price is divided by four. A shareholder with 100 shares at $150 per share would hold 400 shares at $37.50 after the split, with the position value unchanged at $15,000.
What is a reverse stock split?
A reverse stock split consolidates multiple existing shares into fewer shares, raising the price per share proportionally. In a 1-for-10 reverse split, every ten shares become one share worth ten times the previous price. Companies sometimes use reverse splits to lift a low share price, including to meet minimum-price listing requirements on stock exchanges.
Why do companies split their stock?
Companies typically execute forward splits to bring a high share price into a range perceived as more accessible to a broader base of investors, and to align the price with peers. The split itself does not change the company's market capitalization or fundamentals; it only changes the number of shares over which that value is spread.
What happens to dividends and EPS after a split?
Per-share figures are adjusted in proportion to the split: after a 4-for-1 split, the dividend per share and earnings per share are each divided by four, while total dividends paid and total earnings are unchanged. Data providers retroactively adjust historical per-share figures so comparisons across the split date remain consistent.
Références
- U.S. Securities and Exchange Commission, Investor.gov. Stock splits — investor glossary. investor.gov.
- U.S. Securities and Exchange Commission. Reverse stock splits — investor bulletin. sec.gov.
- CFA Institute. Equity Securities and Corporate Actions — CFA Program Curriculum. cfainstitute.org.
- Financial Industry Regulatory Authority (FINRA). Stock splits and what they mean for investors. finra.org.