Stock Split Calculator

How to calculate a stock split

A stock split divides each existing share into multiple new shares without changing your position’s total value. In a 2-for-1 split every share becomes two, and the per-share price is halved. You own more shares at a lower price, but the total dollar value is identical the moment the split takes effect.

Formula: For an X-for-Y split — New Shares = Old Shares × (X ÷ Y); New Price = Old Price × (Y ÷ X).

1. Note your current share count and the latest share price.
2. Identify the split ratio written as X-for-Y (2-for-1 doubles shares; 1-for-10 is a 10× reverse split).
3. Multiply your shares by X ÷ Y to get the new share count.
4. Multiply the price by Y ÷ X to get the new price — the product (shares × price) stays the same.
5. Optionally divide your original cost per share by the ratio to get the split-adjusted cost basis.

Worked example

You own 10 shares at $100 — a $1,000 position. The company announces a 2-for-1 split. After the split: new shares = 10 × 2/1 = 20, new price = $100 × 1/2 = $50. Total value = 20 × $50 = $1,000. Same money, twice the shares, half the price.

Forward split vs reverse split

A forward split increases the share count (e.g. 2-for-1, 3-for-1, 4-for-1). It is usually a sign of confidence — the company has run its share price high enough that splitting makes shares more accessible to retail investors. A reverse split decreases the share count (e.g. 1-for-10, 1-for-20). Reverse splits are typically defensive moves: keeping the share price above an exchange minimum (often $1 on the NYSE/Nasdaq) or signalling a higher per-share price to institutions. For a detailed breakdown of common ratios, see our guide to stock split ratios.

How splits affect your portfolio

On the split date your brokerage will adjust your position automatically — you do not need to do anything. Your cost basis per share also adjusts proportionally so that your total basis stays the same. Per-share dividends and EPS adjust by the same ratio, so your dividend income and the company's reported earnings per share both move with the new share count. If a stock has split multiple times, use a cumulative split multiplier to trace the full adjustment back to your original purchase price.

Fractional shares and cash-in-lieu

A fractional split ratio (e.g. 3-for-2) can leave you with a fractional share — for example, 5 shares becomes 7.5 shares. Most brokerages settle the half-share in cash at the post-split price (called "cash-in-lieu"), which is a small taxable sale reported on your 1099. Some modern brokerages hold the fractional share instead.

Splits do not change fundamentals

A split is purely cosmetic accounting. It does not change market cap, earnings, free cash flow, debt, or the long-term outlook for the business. Studies have found small, short-term price bumps after high-profile splits — likely a sentiment effect, not a fundamental one.

Splits are mechanics, not magic

Use this calculator to confirm exactly what your portfolio will look like the morning after a split. Then judge the company on the things that actually change value — earnings, growth, and balance sheet — not the share count.