Calculate percent of a number, percent change, discounts, increases, and part-of-total percentages.
Use the mode that matches the question: percent of a value, part of a total, increase/discount, or change between two values. The result is arithmetic only and does not include taxes, fees, or store and contract rounding rules.
Core formulas: percent of a value = value x percent / 100; part as percent of total = part / total x 100; percentage change = (new - original) / |original| x 100. For increases and decreases, the change amount is added to or subtracted from the starting value.
If you choose percent of a number and enter 15% of 200, the calculator returns 30. If 30 is the part and 200 is the total, the share is 15%. If 200 increases by 15%, the final value is 230.
The calculator treats percent as a ratio per 100. Totals and original values cannot be zero in modes that divide by those values. Results are arithmetic estimates and do not include taxes, fees, store rounding, or contract-specific rules.
Sources support percent as a ratio, percent equations, discounts, and common percent application patterns.
Use these related calculators when percentages affect project cost, pricing, or material planning.
Last reviewed: 6/30/2026