Stock Split Calculator

Calculate post-split shares and adjusted cost basis for forward & reverse splits

What is a Stock Split?

A stock split changes the number of shares you own without changing your total investment value. Forward splits (e.g., 4:1) increase shares and decrease price. Reverse splits (e.g., 1:10) decrease shares and increase price.

Use this calculator to find your post-split shares and adjusted cost basis for tax purposes.

How to use:
1 Select Forward Split (shares increase) or Reverse Split (shares decrease)
2 Choose the Split Ratio or enter a custom ratio
3 Enter your Pre-Split Shares and optionally purchase price/current price
4 View your Post-Split Shares, adjusted cost basis, and new price
Split Type
Forward Split: Company increases shares outstanding. You receive more shares at a lower price per share. Example: NVDA 10:1 split in 2024.
Split Ratio
:
4:1 means you receive 4 new shares for every 1 old share. Also written as "4-for-1" split.
Your Position
Number of shares you own before the split.
$
Original cost basis for tax calculation.
$
Pre-split market price per share.

Results

Post-Split Shares
—
Your new share count after the split
Adjusted Cost Basis
—
New cost per share for tax purposes
New Stock Price
—
Expected price after split
Total Value (Before)
—
Position value pre-split
Total Value (After)
—
Unchanged by the split
Enter Shares Owned to calculate post-split results.

Calculation Breakdown

Split Ratio: 4:1 (Forward)

Formula: Post-Split Shares = Pre-Split Shares × 4

Result: —

Understanding Stock Splits

A stock split is a corporate action that adjusts the number of outstanding shares without changing the company's total market value. Understanding splits is essential for tracking your cost basis and making informed investment decisions.

Important: Stock splits do NOT change the total value of your investment. If you had $10,000 before the split, you still have $10,000 after. The split is cosmetic — it changes share count and price proportionally.

Forward Stock Split Example

NVIDIA 10:1 Split (June 2024):

• Before: 100 shares × $1,200/share = $120,000

• After: 1,000 shares × $120/share = $120,000

• Cost basis adjusted: $500/share → $50/share

Reverse Stock Split Example

1:10 Reverse Split:

• Before: 1,000 shares × $2/share = $2,000

• After: 100 shares × $20/share = $2,000

• Cost basis adjusted: $5/share → $50/share

Why Do Companies Split Stock?

Forward Split Reasons Reverse Split Reasons
Make shares more affordable for retail investors Meet exchange minimum price requirements ($1+ for NASDAQ)
Increase trading liquidity Attract institutional investors with price minimums
Qualify for price-weighted indices (like Dow Jones) Reduce administrative costs (fewer shares to track)
Psychological appeal of "lower" share price Improve perceived legitimacy (penny stocks)

Recent Notable Stock Splits

Company Symbol Split Ratio Year
NVIDIA NVDA 10:1 2024
Amazon AMZN 20:1 2022
Alphabet (Google) GOOGL 20:1 2022
Tesla TSLA 3:1 2022
Apple AAPL 4:1 2020

Key Terms

Cost Basis

Original purchase price per share, used to calculate capital gains when you sell. Must be adjusted after splits for accurate tax reporting.

Fractional Shares

Partial shares that may result from reverse splits. Brokers typically pay cash-in-lieu or allow fractional share ownership.

Frequently Asked Questions

A stock split is a corporate action where a company divides its existing shares into multiple shares. In a forward split (like 4:1), you receive 4 shares for every 1 share you own, but each share is worth 1/4 of the original price. Your total investment value remains exactly the same. Companies split stock to make shares more affordable and increase liquidity.

A reverse stock split consolidates existing shares into fewer shares. In a 1:10 reverse split, every 10 shares become 1 share, but each share is now worth 10x more. Your total investment value stays the same. Companies do reverse splits to increase share price, often to meet stock exchange minimum price requirements or attract institutional investors.

A reverse split is often viewed negatively because it typically indicates a company is struggling to maintain minimum share price requirements. However, it's not always bad — some healthy companies do reverse splits to attract institutional investors who have minimum share price requirements. The split itself doesn't change company fundamentals or your investment value.

Divide your original cost basis by the split ratio for forward splits, or multiply for reverse splits. For a 4:1 forward split: if you bought at $100/share, your new cost basis is $100 ÷ 4 = $25/share. For a 1:10 reverse split: if you bought at $5/share, your new cost basis is $5 × 10 = $50/share. This is crucial for calculating capital gains taxes.

No, a stock split itself is not a taxable event because your total investment value doesn't change. You only owe taxes when you eventually sell the shares for a gain. However, you must adjust your cost basis per share for accurate tax reporting when you do sell. In reverse splits, if you receive cash for fractional shares, that portion may be taxable.

In a reverse split, if you don't own enough shares to convert evenly, you may receive fractional shares or cash-in-lieu. For example, in a 1:10 reverse split, if you own 15 shares, you'd get 1 full share plus either 0.5 fractional shares or a cash payment for the remaining 5 pre-split shares. Policies vary by broker.

NVIDIA executed a 10-for-1 forward stock split in June 2024 when shares were trading above $1,000. The split made shares more accessible to retail investors and enabled potential inclusion in price-weighted indices. After the split, shares traded around $100-120, making it easier for individual investors to buy whole shares.

No. A stock split does not change your total investment value. It only changes the number of shares you own and the price per share. If you had $10,000 worth of stock before a split, you still have $10,000 worth after. The split is purely cosmetic — it doesn't affect the company's market capitalization, your ownership percentage, or the fundamentals of the business.
Disclaimer: This calculator is for educational and informational purposes only. It should not be considered investment, tax, or legal advice. Always verify split details with your broker and consult a tax professional for cost basis adjustments. Stock splits are announced by companies and may have specific record dates and effective dates that affect your shares.

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Quick Reference

Forward Split: More shares, lower price
Reverse Split: Fewer shares, higher price
4:1 Split: 4 shares per 1 owned
1:10 Reverse: 1 share per 10 owned
Total Value: Stays the same

Notable Splits

NVDA 10:1 (June 2024)

GOOGL 20:1 (July 2022)

AMZN 20:1 (June 2022)

TSLA 3:1 (Aug 2022)

AAPL 4:1 (Aug 2020)

Tax Tip

Stock splits are not taxable events. However, you must adjust your cost basis per share for accurate capital gains calculations when you sell. Keep records of all splits.