What "calculating stock" means and why you need to do it

Calculating stock means finding out what your shares are worth right now, what you paid for them, and how much money you've made or lost. You do this by multiplying the current price per share by the number of shares you own, then comparing that to what you originally spent. This is how you know whether your investment is up or down, and it's the foundation for understanding your portfolio's performance.

You need these numbers for three reasons: to know your net worth, to decide whether to buy or sell, and to report gains or losses to the IRS at tax time. Without calculating, you're flying blind on one of your largest assets.

Key Takeaways

  • Current stock value equals the share price times the number of shares you own, and you can find current prices on your brokerage account, Yahoo Finance, or Google Finance.
  • Your cost basis is the total amount you paid for all your shares, including commissions, and you need this to calculate your gain or loss.
  • Gain or loss is the difference between what you sold for (or what it's worth now) and what you paid, and the IRS requires you to report this on Schedule D.
  • If you bought shares at different times and prices, you must track which shares you sold using one of four IRS-approved methods: FIFO, LIFO, average cost, or specific identification.
  • Most brokerages now calculate and report this for you, but understanding the math yourself prevents errors and helps you make better decisions.

Finding the current price and calculating what your shares are worth today

The current price of a stock is the last price it traded at during market hours. You can find it on your brokerage account (Fidelity, Vanguard, Charles Schwab, E-Trade, or wherever you hold the shares), on Yahoo Finance, Google Finance, or the company's investor relations website. The price updates throughout the trading day when the market is open, and stays the same after 4 p.m. Eastern until the next market open.

To find what your shares are worth right now, use this formula:

Current Value = Current Share Price × Number of Shares You Own

For example: if you own 50 shares of a stock trading at $120 per share, your current value is $120 × 50 = $6,000. If the price moves to $125, your value becomes $125 × 50 = $6,250. Your brokerage account usually shows this calculation automatically in your holdings list, but doing it yourself confirms the math is right.

Calculating your cost basis: what you actually paid

Cost basis is the total amount of money you spent to buy your shares, including the purchase price and any commissions or fees. If you bought all your shares at once, the math is simple: multiply the price per share by the number of shares, then add any commission. If you bought shares multiple times at different prices, you add up all those purchases.

Example: You buy 30 shares at $100 each with a $10 commission. Your cost basis is (30 × $100) + $10 = $3,010. Later you buy 20 more shares at $110 each with a $10 commission. Your total cost basis is now $3,010 + (20 × $110) + $10 = $5,230.

Your brokerage keeps a record of your cost basis for every purchase. You can find it in your account statements or in a section labeled "Tax Lot" or "Cost Basis." If you bought through a dividend reinvestment plan (DRIP) or received shares as a gift or inheritance, the cost basis rules are different — your brokerage will note this separately.

Computing your gain or loss when you sell or check your portfolio

Your gain or loss is the difference between what you sold the shares for (or what they're worth now if you still own them) and your cost basis. This is the number that matters for taxes and for knowing whether your investment worked out.

Gain or Loss = Current Value − Cost Basis

If the number is positive, you have a gain. If it's negative, you have a loss. Example: You paid $3,010 for 30 shares (cost basis). You sell them when the price is $110 per share, so you receive 30 × $110 = $3,300. Your gain is $3,300 − $3,010 = $290.

If you still own the shares and just want to know how you're doing, use the current value instead of the sale price. If your 30 shares are now worth $3,500 total, your unrealized gain is $3,500 − $3,010 = $490. This gain is "unrealized" because you haven't sold yet — it only becomes real (and taxable) when you actually sell.

Tracking multiple purchases and which shares you're selling

If you bought the same stock at different times and prices, you need to decide which shares you're selling when you sell only part of your position. The IRS allows four methods, and the one you choose affects how much tax you owe.

FIFO (First In, First Out) assumes you sell the oldest shares first. This is the default method if you don't specify anything else. LIFO (Last In, First Out) assumes you sell the newest shares first, which can lower your tax bill if prices have risen. Average cost divides your total cost basis by the total number of shares to find an average price per share, then uses that for all sales. Specific identification lets you choose exactly which shares you're selling, which gives you the most control but requires detailed record-keeping.

Most brokerages default to FIFO, but you can usually change this in your account settings or by telling your broker which method you want to use before you sell. Your choice must be consistent across all sales of that stock in the same account, and you must document it. If you don't specify, the IRS assumes FIFO.

Using a spreadsheet or your brokerage tools to track everything

You can calculate stock value by hand with a calculator, but a spreadsheet is faster and less error-prone, especially if you own multiple stocks or have made many purchases. Create columns for the stock symbol, purchase date, number of shares, price per share, total cost (including commission), current price, current value, and gain or loss. Most spreadsheet programs (Google Sheets, Excel) have built-in formulas that do the multiplication and subtraction for you.

Your brokerage account already does most of this work. Log in and look for a section called "Holdings," "Portfolio," "Positions," or "My Stocks." It will show you the current value of each stock, your cost basis, and your gain or loss — usually both the dollar amount and the percentage. Some brokerages also show you the date you bought each lot and the cost per share, which is helpful if you need to calculate taxes later.

If you use a tax software like TurboTax or H&R Block, you can import your brokerage data directly, and the software will calculate your gains and losses for you. This is the easiest route if you sold shares during the year and need to report them on your tax return.

Understanding the difference between realized and unrealized gains

An unrealized gain is the profit you have on paper while you still own the stock. An realized gain is the profit you lock in when you actually sell. The IRS only taxes realized gains — you don't owe anything on unrealized gains, no matter how large they are.

This matters because it changes how you think about selling. If a stock has gone up $5,000 but you still own it, you have an unrealized gain of $5,000 and owe no tax. The moment you sell, that $5,000 becomes real and you owe tax on it (unless you held it for less than a year, in which case it's taxed as ordinary income; if you held it for more than a year, it gets the lower long-term capital gains rate). This is why some people hold losing stocks — they're waiting for them to recover so they don't have to realize the loss, or they're avoiding the tax hit from selling winners.

Frequently Asked Questions

Do I need to include dividends in my cost basis?

No. Dividends are separate from cost basis. Your cost basis is only what you paid to buy the shares. If you reinvested dividends to buy more shares, those new shares have their own cost basis equal to what the dividend was worth on the day you reinvested it. Your brokerage tracks this separately.

What if I inherited stock or received it as a gift?

Inherited stock gets a "stepped-up basis," meaning your cost basis is the stock's value on the date the person died, not what they paid for it. Gifted stock keeps the original owner's cost basis. Your brokerage will note this in your records — ask them if you're unsure.

How do I calculate stock value if I own fractional shares?

The same way: multiply the current price by the number of shares, including the decimal. If you own 10.5 shares at $100 per share, your value is $100 × 10.5 = $1,050. Most brokerages now allow fractional shares and calculate this automatically.

Do I have to report unrealized gains on my taxes?

No. You only report realized gains and losses — the ones from shares you actually sold. Unrealized gains are not taxable until you sell. Keep records of your cost basis so you can calculate the gain or loss when you do sell.

What if my brokerage closed and I can't find my cost basis records?

Contact the brokerage directly, even if it's closed — records are usually kept for years. If you can't reach them, the IRS allows you to reconstruct cost basis using old statements, trade confirmations, or bank records. Keep whatever documentation you have and explain the situation on your tax return if needed.