You wake up, check your portfolio, and your stomach drops. The stock you bought at $1,200 per share now shows $120. You own ten times more shares than yesterday. Did something go horribly wrong?
No. Your company just did a stock split. Your investment is worth exactly what it was yesterday.
That split-second panic when the numbers look "wrong" is almost universal — even experienced investors double-take. This stock split calculator eliminates the guesswork. Enter your shares, the share price, and the split ratio, and you'll see exactly what your holdings look like after any forward or reverse stock split.
What Is a Stock Split?
A stock split changes the number of shares you own and the price per share — without touching your total investment value. That's it. That's the whole concept.
Picture a pizza. You can slice it into 4 large pieces or 8 smaller ones. Either way, you have the same amount of pizza. Stock splits work the same way.
In a 2-for-1 split, every share you own becomes two shares at half the price. A 10-for-1 split gives you ten shares for every one, each worth a tenth of the original. Your portfolio balance? Identical.
There are two types:
- Forward splits increase your share count (the common, usually positive kind)
- Reverse splits decrease your share count (the kind that raises eyebrows)
Both preserve your total investment value. The difference is what they signal about the company.
How Forward Stock Splits Work
A forward split multiplies your shares while dividing the price. Companies do this for one main reason: their stock price got too high for everyday investors to comfortably buy.
When a single share costs $2,000, a lot of people can't — or won't — buy it. Even with fractional share trading available at most brokerages, there's a psychological barrier. Investors like owning whole shares. Companies know this.
That's why NVIDIA did a 10-for-1 split when shares hit $1,200. It's why Amazon split 20-for-1 at $2,000+. It's why Apple has split five times since going public. These companies weren't in trouble — they were making their stock more accessible.
Split Ratio | Each Share Becomes | Price Per Share |
|---|---|---|
2-for-1 | 2 shares | Halved |
3-for-1 | 3 shares | Cut to 1/3 |
4-for-1 | 4 shares | Cut to 1/4 |
10-for-1 | 10 shares | Cut to 1/10 |
20-for-1 | 20 shares | Cut to 1/20 |
The signal: Forward splits usually mean a stock has been performing well. They're not a guarantee of future returns, but they're generally a sign of confidence from company leadership.
How Reverse Stock Splits Work
Reverse splits go the other direction. They combine your shares into fewer, higher-priced shares. A 1-for-10 reverse split turns every 10 shares you own into 1 share at 10 times the price.
Why would a company do this? Usually because their stock price has dropped dangerously low.
The NYSE and NASDAQ both have minimum price requirements — typically $1 per share. If a stock trades below that threshold for too long, the company faces delisting. A reverse split boosts the share price above the minimum to stay listed.
Reverse Ratio | Shares Combined | Price Per Share |
|---|---|---|
1-for-5 | Every 5 → 1 | Multiplied by 5 |
1-for-10 | Every 10 → 1 | Multiplied by 10 |
1-for-20 | Every 20 → 1 | Multiplied by 20 |
Here's where context matters. A reverse split doesn't destroy value — your investment total stays the same. But a company reverse-splitting because its stock fell from $50 to $0.30 is telling you something about its trajectory. That said, not every reverse split is a red flag. GE did a 1-for-8 reverse split in 2021 as part of a major restructuring that ultimately led to a successful breakup into three companies.
Bottom line: Forward splits happen when things are going right. Reverse splits happen when a company needs to reset. Look at the why, not just the what.
How to Use This Calculator
- Enter your shares — How many shares do you currently own? Type that number in "Number of Shares (Before Split)."
- Enter the share price — The current price per share goes in "Share Price (Before Split)."
- Set the split ratio:
- For a 2-for-1 forward split: enter 2 in "New Shares" and 1 in "Existing Shares"
- For a 1-for-10 reverse split: enter 1 in "New Shares" and 10 in "Existing Shares"
- See your results — Your post-split share count and adjusted price appear instantly.
Quick tip: When a company announces a "4-for-1 split," the first number always goes in "New Shares" and the second in "Existing Shares."
Stock Split Formulas
Two formulas. Both are simple.
Shares after split:
New Shares = Original Shares x (New / Existing)
Price after split:
New Price = Original Price x (Existing / New)
Worked example — 3-for-1 forward split:
- You own 150 shares at $300 each ($45,000 total)
- New shares: 150 x 3 = 450 shares
- New price: $300 / 3 = $100
- Portfolio value: 450 x $100 = $45,000 ✓
Worked example — 1-for-10 reverse split:
- You own 2,000 shares at $0.80 each ($1,600 total)
- New shares: 2,000 / 10 = 200 shares
- New price: $0.80 x 10 = $8.00
- Portfolio value: 200 x $8.00 = $1,600 ✓
The total never changes. If your math gives you a different portfolio value before and after, something's off.
Real-World Stock Split Examples
The Long-Term Holder: NVIDIA 10-for-1 (2024)
Marcus bought 50 shares of NVIDIA in early 2023 at $180 each — a $9,000 investment. By the time the 10-for-1 split was announced in mid-2024, those shares were trading around $1,200 each. His $9,000 had grown to $60,000.
After the split: 500 shares at $120 each. Still $60,000. But now Marcus could sell in smaller increments without liquidating a $1,200 block, and his friends who'd been priced out could finally buy in.
The Retirement Investor: Apple 4-for-1 (2020)
Diana had been buying Apple stock in her IRA for years — 100 shares at an average cost of $85 each. When Apple announced its 4-for-1 split with shares around $500, her 100 shares became 400 shares at roughly $125 each.
Her total investment value didn't budge. But her adjusted cost basis per share dropped from $85 to $21.25 — an important number for when she eventually starts taking distributions.
The Accessibility Play: Amazon 20-for-1 (2022)
At $2,000+ per share, Amazon was one of the most expensive stocks in the S&P 500. Their 20-for-1 split turned each share into 20 at around $100 each. Kevin, a college student investing $200 a month, went from being unable to afford a single share to being able to buy whole shares regularly. Same company, same market cap — just more accessible.
The Restructuring: GE 1-for-8 Reverse Split (2021)
General Electric's reverse split told a different story. After years of declining performance, GE consolidated 8 shares into 1. An investor holding 800 shares at $10 ended up with 100 shares at $80. Same $8,000 value — but GE was simplifying its share structure before breaking into three separate companies. The reverse split was part of a forward-looking strategy, not a distress signal.
Notable Stock Splits in History
Company | Year | Split Ratio | Pre-Split Price (Approx.) | Post-Split Price (Approx.) |
|---|---|---|---|---|
NVIDIA | 2024 | 10-for-1 | $1,200 | $120 |
Amazon | 2022 | 20-for-1 | $2,447 | $122 |
Alphabet (Google) | 2022 | 20-for-1 | $2,254 | $113 |
Tesla | 2022 | 3-for-1 | $891 | $297 |
Apple | 2020 | 4-for-1 | $500 | $125 |
Tesla | 2020 | 5-for-1 | $2,213 | $443 |
Apple | 2014 | 7-for-1 | $645 | $92 |
GE (Reverse) | 2021 | 1-for-8 | $10 | $80 |
Pattern worth noting: Most forward splits land the share price in the $100–$150 range. Companies seem to agree that's the sweet spot for retail investor accessibility.
Common Mistakes Investors Make With Stock Splits
Mistake
Your portfolio shows a stock at half the price it was yesterday. If you don't realize a 2-for-1 split just happened, you might sell in a panic — locking in your position, potentially triggering taxes, and missing future upside. Always check for recent split announcements before reacting to sudden price changes.
Mistake
After Apple's 4-for-1 split, the stock dropped from ~$500 to ~$125. Some investors saw $125 and thought it was a bargain. But the company's market cap hadn't changed at all. A $125 post-split share represents the exact same ownership stake as a $500 pre-split share. The stock isn't cheaper. It's just sliced differently.
Mistake
This one can be expensive. Say you bought 100 shares at $200 and the stock does a 2-for-1 split. Your cost basis per share drops to $100. If you forget this and sell 200 shares at $150, you might report a $50 loss per share ($150 - $200) instead of the correct $50 gain per share ($150 - $100).
On 200 shares, that's the difference between reporting a $10,000 loss and a $10,000 gain — a $20,000 swing in reported income. The IRS will notice.
Mistake
Yes, many companies reverse-split because they're struggling. But not all. GE's 2021 reverse split preceded a successful three-way breakup. Judge the company's fundamentals and strategy, not the split mechanics.
How Stock Splits Affect Your Cost Basis
Stock splits aren't taxable events. The IRS doesn't care that your share count changed — no gain or loss was realized. But your cost basis per share absolutely changes, and getting this wrong costs real money.
The formula:
Adjusted Cost Basis Per Share = Original Cost Per Share x (Existing / New)
Example: You bought 100 shares at $400 each. After a 4-for-1 split, you own 400 shares. New cost basis: $400 / 4 = $100 per share. Total cost basis is still $40,000.
Where people really mess up: Stocks that have split multiple times. If you bought Apple in 2010 at $40 per share (pre-split), it has since gone through a 7-for-1 split (2014) and a 4-for-1 split (2020). Your adjusted cost basis per share: $40 / 7 / 4 = roughly $1.43 per share. Selling a share at $190 using your original $40 cost basis would underreport your gain by about $148 per share.
Most brokerages handle this automatically. But if you've transferred accounts, inherited stock, or kept your own records, double-check the math.