Stock Split Calculator
Calculate your post-split share count, adjusted price, and cost basis for any forward or reverse stock split. Supports ratios from 2:1 to 25:1 forward splits and 1:2 to 1:20 reverse splits, including notable splits like Apple 4:1, Tesla 5:1, NVIDIA 10:1, Amazon 20:1, and Booking 25:1.
Stock Split Calculator
Calculate post-split shares, adjusted share price, and cost basis.
Frequently Asked Questions
What is a stock split?
A stock split is a corporate action where a company divides existing shares into more shares while lowering the price per share proportionally. The total market value stays the same. For example, in a 2-for-1 split, each share becomes two shares at half the original price.
How does a stock split affect share price?
A stock split lowers the price per share in line with the split ratio while increasing the number of shares you hold. In a 3-for-1 split, a $300 stock becomes $100 per share, but you hold three times as many shares. Your total investment value stays the same immediately after the split.
What is a 2-for-1 stock split?
A 2-for-1 (2:1) stock split means every share you own becomes two shares, each worth half the original price. If you owned 100 shares at $200 each, after the split you would own 200 shares at $100 each. This is the most common split ratio.
Do I lose money in a stock split?
No. A stock split does not change the total value of your investment. You receive more shares at a proportionally lower price, so the math balances out. Your ownership percentage in the company also stays the same.
What is a reverse stock split?
A reverse stock split combines multiple shares into fewer shares at a higher price per share. In a 1-for-10 reverse split, every 10 shares become 1 share worth 10 times as much. Companies often use reverse splits to increase their share price or meet exchange listing requirements.
Why do companies split their stock?
Companies split their stock to make shares more affordable for retail investors and to improve trading liquidity. A lower share price can attract more individual investors and reduce bid-ask spreads. Some companies also split to qualify for price-weighted indexes.
How do I calculate shares after a split?
Multiply your current shares by the split ratio. For a forward split like 3-for-1, multiply by 3. For a reverse split like 1-for-5, divide by 5. New Shares = Current Shares × (Split Ratio Numerator / Split Ratio Denominator).
How do I calculate my new cost basis after a stock split?
Adjusted Cost Basis = Original Purchase Price ÷ Split Ratio. For a 4:1 split on shares bought at $400, the new cost basis is $100 per share. Your total cost stays unchanged; only the per-share basis adjusts.
Do I owe taxes on a stock split?
No, stock splits are generally not taxable events in the US. The IRS treats them as adjustments, not sales. However, your cost basis per share changes, which matters when you later sell. Cash received instead of fractional shares during a reverse split may be taxable.
What happens to fractional shares in a reverse split?
If a reverse split creates fractional shares, your broker usually either sells the fractional portion and pays cash, or rounds to the nearest whole share. Cash-in-lieu payments are generally treated as taxable capital gains.
Is a reverse stock split good or bad?
It depends on the context. Companies often use reverse splits to meet exchange minimum price requirements, which can signal financial trouble. Some healthy companies use them to attract institutional investors or reduce share count.
How does a stock split affect dividends?
Dividends per share adjust proportionally after a split. In a 2:1 split, a $2 dividend becomes $1 per share. Because you hold twice as many shares, your total dividend income stays the same immediately after the split.
How to Calculate a Stock Split
A stock split changes the number of shares you own and the price per share, but not the total value of your holdings. Use the formulas below to work out the new share count, post-split price, and adjusted cost basis.
Core Formulas
These three formulas cover most stock split calculations.
New Share Count
New Shares = Current Shares × Split Ratio
For a 4:1 split with 100 shares: 100 × 4 = 400 shares.
New Price Per Share
New Price = Current Price ÷ Split Ratio
For a 4:1 split at $500/share: $500 ÷ 4 = $125/share.
Adjusted Cost Basis
Adjusted Cost Basis = Purchase Price ÷ Split Ratio
Bought at $400, 4:1 split: $400 ÷ 4 = $100 per share cost basis.
Forward vs Reverse Stock Split
Forward splits increase the share count and lower the price. Reverse splits do the opposite.
| Feature | Forward Split | Reverse Split |
|---|---|---|
| Share count | Increases | Decreases |
| Price per share | Decreases | Increases |
| Total value | Unchanged | Unchanged |
| Common ratios | 2:1, 3:1, 4:1, 10:1, 20:1 | 1:2, 1:5, 1:10, 1:20 |
| Signal | Often positive (high growth) | Often negative (compliance) |
| Example companies | Apple, NVIDIA, Amazon | Struggling companies, SPACs |
Recent Notable Stock Splits
Major tech and growth companies have executed large stock splits in recent years to make their shares more accessible to retail investors.
| Company | Symbol | Ratio | Year | Pre-Split Price |
|---|---|---|---|---|
| Apple | AAPL | 4:1 | 2020 | ~$500 |
| Tesla | TSLA | 5:1 | 2020 | ~$2,200 |
| Tesla | TSLA | 3:1 | 2022 | ~$900 |
| Amazon | AMZN | 20:1 | 2022 | ~$2,800 |
| Alphabet | GOOGL | 20:1 | 2022 | ~$2,800 |
| NVIDIA | NVDA | 10:1 | 2024 | ~$1,200 |
| Netflix | NFLX | 10:1 | 2025 | ~$2,000 |
| Booking Holdings | BKNG | 25:1 | 2026 | ~$5,000 |
Cost Basis After a Stock Split
When a stock splits, your cost basis per share adjusts proportionally while your total cost stays the same. This matters for calculating capital gains when you sell.
Worked Example: Apple 4:1 Split (2020)
- You bought 50 shares of AAPL at $300 each (total cost: $15,000).
- Apple announces a 4:1 stock split.
- After the split: 50 × 4 = 200 shares.
- Adjusted cost basis: $300 ÷ 4 = $75 per share.
- Total cost basis: 200 × $75 = $15,000 (unchanged).
- If you sell at $150/share, your gain per share = $150 - $75 = $75.
Tax Implications of Stock Splits
Forward Splits
Forward stock splits are not taxable events. The IRS treats them as a reclassification of existing shares, not a disposition. You simply adjust your cost basis per share and your holding period remains unchanged. No Form 1099 is issued for the split itself.
Reverse Splits
Reverse stock splits are also not taxable events in most cases. However, if you receive cash in lieu of fractional shares, that cash payment is generally treated as a taxable capital gain.
Record-keeping tip: Always update your cost basis records after a stock split. Your broker should adjust the cost basis automatically in your account, but verify the numbers match your records. Accurate cost basis tracking is essential for reporting capital gains and losses on your tax return (Schedule D).
What Happens to Fractional Shares
Reverse stock splits can create fractional shares when your share count does not divide evenly by the split ratio. For example, 75 shares in a 1:10 reverse split produces 7.5 shares.
How Brokers Handle Fractional Shares
- Cash-in-lieu: The broker sells the fractional portion on the open market and credits your account with cash. This is the most common approach.
- Rounding: Some brokers round up or down to the nearest whole share, though this is less common.
- Fractional share support: Brokers that support fractional shares may simply keep the fractional position in your account.
Cash-in-lieu payments are treated as taxable capital gains. The gain or loss is calculated as the cash received minus the cost basis of the fractional share. This amount is reported on Form 1099-B.
How Stock Splits Affect Dividends
Dividends per share adjust proportionally after a split, just like the stock price. Your total dividend income remains the same immediately after the split.
Example: 2:1 Split and Dividends
- Before split: 100 shares, $2.00 dividend per share = $200 total quarterly dividend.
- After 2:1 split: 200 shares, $1.00 dividend per share = $200 total quarterly dividend.
- Your total income is unchanged.
If the company later increases the adjusted dividend (for example, from $1.00 to $1.20 per share), that represents a genuine 20% dividend raise, separate from the split adjustment.