Stock Split Calculator

The Stock Split Calculator estimates how a forward or reverse stock split changes your share count, adjusted price per share, total position value, and cost basis per share. It is useful when reading corporate action notices, checking brokerage statements, comparing historical stock charts, or planning around employee equity and long-term holdings.

How to Use

1. Enter the number of shares you own and the current or pre-split share price.
2. Use the new-for-old ratio from the company announcement, such as 2-for-1, 3-for-2, or 1-for-10.
3. Select whether fractional shares should be kept, paid as estimated cash in lieu, or rounded down without a cash adjustment.
4. Optionally enter your pre-split cost basis per share to estimate the adjusted cost basis per share after the split.
5. Compare pre-split and post-split shares, price, market value, fractional share treatment, and common split scenarios.

Stock Split Formula

Forward vs Reverse Stock Splits

A forward split increases the share count and reduces the price per share by the same ratio. A 2-for-1 split turns 100 shares into 200 shares and cuts a $50 share price to $25, before market movement.

A reverse split consolidates shares and raises the price per share by the inverse ratio. A 1-for-10 reverse split turns 1,000 shares into 100 shares and raises a $0.80 share price to $8, before market movement.

FAQ

What does a stock split calculator do?

It converts your current share count and pre-split price into the expected post-split share count and adjusted price using the announced split ratio. It also checks that the total position value is unchanged before fractional share rounding.

How do I read a 3-for-2 stock split?

In a 3-for-2 split, every 2 old shares become 3 new shares. Share count is multiplied by 3 ÷ 2, while the share price is multiplied by 2 ÷ 3.

What happens in a reverse stock split?

In a reverse stock split, multiple old shares are consolidated into fewer new shares. A 1-for-10 reverse split divides the share count by 10 and multiplies the price per share by 10, before any market movement.

Does a stock split change my investment value?

A stock split by itself does not create or destroy value. The number of shares and price per share adjust in opposite directions, so the theoretical market value remains the same before taxes, fees, trading movement, and fractional share handling.

How are fractional shares handled after a split?

Fractional share treatment depends on the broker and company action. Some accounts keep fractional shares, while others round down and pay cash in lieu based on the post-split price.

How does a stock split affect cost basis?

Total cost basis usually stays the same, but cost basis per share adjusts by the inverse of the split ratio. For example, a 2-for-1 split halves the per-share basis, while a 1-for-5 reverse split multiplies it by 5.