THE NUMORIX GUIDE
How to use the Stock Calculator
Last reviewed September 14, 2026
What this calculator does
The engine calculates total cost = purchase price x shares and total return = selling price x shares.
Formula and method
The engine calculates total cost = purchase price x shares and total return = selling price x shares. Profit or loss is total return - total cost, and percent return is profit or loss / total cost x 100.
Variables and inputs
Enter purchase price per share, number of shares, and selling price per share. The UI requires positive prices and shares and parses shares as an integer. The route does not request purchase dates, dividends, commissions, taxes, or currency.
Worked example
For 100 shares bought at $50 and sold at $75, total cost is $5,000, total return is $7,500, profit is $2,500, and percent return is $2,500 / $5,000 x 100 = 50.00%.
How to interpret the result
The result is a price-only holding-period return before costs and taxes. It can describe a realized sale or a hypothetical exit, but it is not annualized and does not include cash distributions unless they are folded into the selling price.
Common mistakes to avoid
Use per-share prices and the same number of shares for both transactions. Do not call total return profit; the original cost is still part of the returned cash. Add commissions, dividends, splits, and taxes separately when comparing with an account statement.
Assumptions and limitations
The calculation omits holding period, dividend income, reinvestment, fees, taxes, fractional shares, splits, currency changes, and market liquidity. A zero purchase cost would make percent return undefined in the engine, so the UI prevents nonpositive purchase prices.
Practical use and checks
The Stock Calculator checks the simple price return of a fixed number of shares. Enter the purchase price per share, share count, and sale price per share; use it for a quick trade or scenario comparison before adding dividends and transaction costs separately. For example, 40 shares bought at $25 and sold at $31 should show total cost of $1,000, total return of $1,240, profit of $240, and a percentage return of 24%. A useful second check is to keep the 40 shares and enter a sale price of $20: the result should show a $200 loss and a -20% return. The percentage uses original cost as the denominator, so changing the number of shares changes dollars but not the percentage when prices stay fixed. Interpret total return here as sale proceeds, not total investment performance. Dividends, commissions, bid-ask spread, taxes, splits, and currency conversion can change the actual result. The calculator assumes all shares are bought at one price and sold at one price, which is not how recurring purchases or partial sales behave. A zero purchase price makes the percentage undefined, while negative or fractional inputs may produce arithmetic that has no ordinary trading meaning. Use the output as a transparent price-only check and reconcile it with the brokerage statement before evaluating a real gain or loss.