股票拆分计算器
计算任意正向或反向股票拆分后的持股数量、调整后价格和持仓成本。支持 2:1 至 25:1 的正向拆分和 1:2 至 1:20 的反向拆分，包括苹果 4:1、特斯拉 5:1、英伟达 10:1、亚马逊 20:1 和 Booking 25:1 等知名拆分案例。
Stock Split Calculator
Calculate your new share count, price, and cost basis after a stock split
Frequently Asked Questions
股票分拆是什么？如何计算？
股票分拆是公司将现有股份按比例拆分为更多股份，同时价格按比例降低，股东总持仓价值不变。例如，2:1 分拆：持有 100 股、价格 $200/股的投资者，分拆后持有 200 股、价格 $100/股，总价值仍为 $20,000。
为什么公司要进行股票分拆？
股票分拆的主要原因：降低每股价格，使散户投资者更易负担；提高股票流动性（更多股份、更低单价、交易更活跃）；发出公司股价强劲增长的积极信号；部分指数成分股也会考虑分拆以维持合理价格区间。
反向股票分拆（缩股）是什么？
反向分拆（Reverse Split）是将多股合并为一股，单股价格升高，总持仓价值不变。例如，1:5 反向分拆：100 股、$2/股 → 20 股、$10/股。通常是股价过低（面临退市风险）的公司采取的措施。
股票分拆后如何调整成本基础？
分拆后的每股成本基础 = 原成本基础 / 分拆比例。例如，以 $200/股买入 100 股（总成本 $20,000），2:1 分拆后变为 200 股，每股成本基础调整为 $100。持仓总成本基础不变，仅按股数比例分摊。
How to Calculate a Stock Split
A stock split changes the number of shares you own and the price per share, but your total investment value stays the same. Here are the three formulas you need:
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 shares and lower the price. Reverse splits do the opposite. The table below compares the key differences:
| 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 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 (for example, 15 shares in a 1:10 reverse split creates 1.5 shares, and you receive cash for the 0.5 fractional share), that cash payment is 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 (e.g., from $1.00 to $1.20 per share), that represents a genuine 20% dividend raise, separate from the split adjustment.