Stock Split Calculator

How Stock Splits Work

A stock split increases the number of shares outstanding while proportionally decreasing the price per share. The total market capitalization stays where it was, so you simply hold more pieces of the same pie. Companies split stocks to make shares more accessible to retail investors.

Forward split formula:

New Price = Old Price ÷ Split Ratio New Shares = Old Shares × Split Ratio

Worked example: 3-for-1 split:

• Pre-split price: $450 per share
• Pre-split shares owned: 20
• Split ratio: 3:1

New price = $450 ÷ 3 = $150 per share New shares = 20 × 3 = 60 shares Total value before: 20 × $450 = $9,000 Total value after: 60 × $150 = $9,000 (unchanged)

Reverse split formula (company consolidates shares):

New Price = Old Price × Reverse Ratio New Shares = Old Shares ÷ Reverse Ratio

Example: 1-for-10 reverse split:

A stock at $0.80 does a 1-for-10 reverse split:

New price = $0.80 × 10 = $8.00 If you held 1,000 shares: new holding = 100 shares

Reverse splits are usually a warning sign. Companies do them to avoid being delisted from exchanges that require a minimum stock price, generally $1.00 on both NASDAQ and the NYSE.

Reverse splits are also where the “your value is unchanged” line stops being true. Forward splits divide evenly often enough that nobody notices, but a 1-for-10 reverse split of 105 shares leaves you with 10.5, and you cannot own half a share of most stocks. Brokers handle the remainder by selling it and sending you cash, which means the reverse split quietly triggers a taxable sale you did not choose to make. On a small holding the cash-out can be most of the position: 7 shares through a 1-for-10 becomes 0.7 shares, and some transfer agents round that to zero and cash you out entirely.

The calculator flags the fractional remainder and prices it, rather than rounding it away.

Historical notable splits:

• Apple: 7-for-1 in 2014, 4-for-1 in 2020
• Tesla: 5-for-1 in 2020, 3-for-1 in 2022
• Amazon: 20-for-1 in 2022 (first split since 1999)
• Berkshire Hathaway Class B: 50-for-1 in 2010

Cost basis adjustment:

After a split your cost basis per share adjusts by the same ratio as the price, so the total basis and any capital gains calculation stay where they were. Buy 20 shares at $450 for a $9,000 basis, take a 3-for-1 split, and you hold 60 shares with a basis of $150 each. Still $9,000.

The holding period carries over too, which matters more than the basis arithmetic: the new shares are treated as acquired on the date you bought the original ones, so a split never resets the clock on long-term capital gains treatment. Enter your cost per share above and the calculator adjusts it for you.