Enter a pre-split price, how many shares you hold and the ratio announced, and see both sides rescaled — with the total value held still.
Enter values.
For a ratio of A for B, the two numbers that describe a holding move in opposite directions by the same factor:
post-split price = price × B ÷ A · post-split shares = shares × A ÷ B
Multiply them back together and A and B cancel, so total value is identical before and after; the tool computes both sides and checks they agree to the cent. A split changes no economics. Earnings per share, the price-earnings ratio, your percentage stake and the company's market capitalisation are all untouched. A 4-for-1 split does not create four companies, and $200 afterwards is not a cheaper claim on the assets — it is the same claim cut four ways.
Firms split anyway: a lower headline price is more affordable to retail buyers and can add liquidity, and index providers weigh or screen on price, so share-count mechanics around index inclusion matter for high-priced names. A reverse split runs the same arithmetic backwards and is usually done to lift a quote back above an exchange's minimum-price listing rule. As a documented fact pattern, reverse splits frequently follow a long stretch of poor performance — the ratio responds to the decline rather than reversing it. That is history, not a prediction.
$800.00 and 10 shares at 4 for 1: price becomes 800 × 1 ÷ 4 = $200.00 and shares become 10 × 4 ÷ 1 = 40. Value before $8,000.00, value after $8,000.00, unchanged.
Flip it to 1 for 4 on the same holding: $3,200.00 a share and 2.5 shares. Still $8,000.00 — and now there is a fraction, which is the next section.
Whole-share accounting breaks whenever shares × A ÷ B is not a whole number. Companies usually cash out or round the fraction, and brokers differ on whether you get a cash payment, a rounded-down position or a fractional holding carried forward — ask yours rather than assuming, since a cash-out can be taxable. This is arithmetic only: it ignores the ex-date, after which the old quote stops meaning anything, and it cannot say how the stock trades afterwards. Splits are often read as bullish and reverse splits as warnings; that is sentiment, not mathematics.
No view on any security, and no knowledge of your cost basis, holding period or tax position. A split announcement is not a recommendation to buy or sell. Informational only, not investment advice.