Percentage Calculator | Increase, Decrease, % of a Number
Percentage Calculator
Use the tools below to calculate % of a number, percentage change, increase/decrease, and reverse percentage. Results are instant and mobile-friendly.
✅ Choose a calculation
% of a Number
Calculate X% of Y.
Percentage Change
Calculate the % change from Old to New.
Increase / Decrease by a Percentage
Apply a % increase or decrease to a starting number.
Reverse Percentage
Find the original value before a % increase or decrease.
📌 Formulas used
- X% of Y = (X ÷ 100) × Y
- % change = ((New − Old) ÷ Old) × 100
- Increase by X% = Start × (1 + X ÷ 100)
- Decrease by X% = Start × (1 − X ÷ 100)
- Reverse % (after increase) = Final ÷ (1 + X ÷ 100)
- Reverse % (after decrease) = Final ÷ (1 − X ÷ 100)
❓ Frequently asked questions
What is 20% of 50?
20% of 50 = (20 ÷ 100) × 50 = 10.
What is the percentage increase from 80 to 100?
((100 − 80) ÷ 80) × 100 = 25%.
Can this be used for tax, discounts, or interest?
Yes for quick estimates—verify rules and rounding for official use.
Disclaimer: This calculator is provided for general reference only. Results may be rounded for display and may not be suitable for situations requiring certified calculations, accounting/tax filings, legal or compliance purposes, credit/interest determinations, medical decisions, engineering tolerances, or safety-critical use. You are solely responsible for verifying inputs, formulas, rounding rules, and outcomes for your intended purpose. This page is not affiliated with, endorsed by, or sponsored by any authority or standards body.