How does a stock split change shares and price?
A stock split changes the number of shares and the per-share price in opposite directions under the simple arithmetic shown here. For a 2-for-1 split, each old share corresponds to two new shares, so the modeled share count doubles and the per-share price halves. The SEC illustrates this with 100 shares at $100 becoming 200 shares at $50, with the total market value unchanged by the split itself. This calculator reproduces that relationship for values you enter; the result is not a current quote or a prediction.
Enter the ratio as “new shares for each old shares.” A 3-for-2 split uses 3 new and 2 old shares. A 1-for-5 reverse split uses 1 new and 5 old shares. The ratio factor is new divided by old; therefore the same formulas cover forward and reverse splits. A reverse split can produce fractional arithmetic shares for a particular holding, even if the issuer’s actual processing uses a different method.
What does the unchanged-value result mean?
The before-and-after totals in this worksheet are calculated from the entered share count and price, with no market movement. The SEC explains that a split by itself does not change an existing shareholder’s total market value. In actual trading, prices can move, and the amount shown by a broker may be affected by rounding or the treatment of fractional shares. Do not treat the modeled total as a forecast or a guaranteed account value.
Why check the issuer’s split terms?
Arithmetic alone does not establish whether or when an announced split applies to a holding. Issuer materials may identify separate announcement, record, distribution, effective, and split-adjusted trading dates. Read the issuer’s official notice and relevant filing, and ask the broker or transfer agent how it handles a position that does not divide into a whole number of shares. This page does not determine cash-in-lieu amounts, tax basis, or account processing.
Frequently asked questions
What does a 2-for-1 split do in this calculator?
It multiplies entered shares by 2 and divides the entered per-share price by 2. The modeled total value is unchanged before any market movement.
Can I calculate a reverse split?
Yes. Enter the number of new shares first and the number of old shares second. For a 1-for-5 reverse split, enter 1 new share and 5 old shares.
Does the result tell me what my brokerage account will show?
No. It displays the unrounded mathematical result. Check the issuer’s terms and ask your broker or transfer agent about fractional shares, rounding, and cash in lieu.
Does this confirm that a split is scheduled?
No. Enter a ratio only after checking issuer materials. Use the SEC stock split verification guide to record the filing and separately labeled dates.
Source checked 2026-11-03: SEC, Stock Splits. Its worked example and explanation support the proportional share/price arithmetic; issuer and broker-specific processing remains outside this worksheet.