What is X% of Y, and X is what percent of Y — for discounts, tips, grades, and your share of a profit.
Working a stock or options P&L instead? Use the Stock Profit Calculator for gain, ROI, and commission. Gear we use lives on Picks (Amazon Associates).
Percent means “per hundred.” To find what is X% of Y, convert the percent to a decimal (divide by 100) and multiply: 12% of $850 is 850 × 0.12 = $102. That is the first calculator on this page — the same math you use for a tip, a discount off a price, a fee, sales tax on a subtotal, or a partner’s cut of a deal.
To find X is what percent of Y, divide X by Y and multiply by 100: $102 is what percent of $850? 102 ÷ 850 × 100 = 12%. Use that when you know the dollar piece and need the ownership or contribution rate — for example, your dollar share of a business profit, a raise vs old salary, completed work vs a project budget, or part of a shared bill.
If a project clears $40,000 and your agreement is 25%, take 25% of 40,000 = $10,000 with the first tool. If you already received $10,000 and the pool was $40,000, the second tool shows 25%. Keep the base consistent: percent of profit is not the same as percent of revenue. Say which base you mean before you negotiate, and write it into the agreement so nobody “reinterprets” the denominator later.
Equity splits work the same way once you agree on fully diluted ownership. Vesting cliffs change how much of that percent you have earned; the calculator only does the arithmetic on the numbers you type.
Sale price ≈ original × (1 − discount%). Tip = bill × tip%. Exam score = points earned ÷ points possible × 100. Weight change = (new − old) ÷ old × 100 — negative means loss. None of those need a spreadsheet if you use the two boxes above and keep units straight (do not mix dollars and percents in one field).
For market trades, percent return is (sell − buy − fees) ÷ cost. This page stays general-purpose; the stock profit calculator folds in shares, prices, and commission so ROI matches how brokers report a closed trade. Pure arithmetic lives on the basic calculator; tip scenarios on the tip calculator.
Results show up to four decimal places so small percents (fees, thin margins) stay readable. Rounding for money usually happens at display — banks and POS systems may banker’s-round differently than your phone. Educational math only — not tax, payroll, or investment advice.