Free Online Percentage Calculator
Use the tabs below to quickly solve common percentage problems: percent of a number, what percent one value is of another, percentage change, and adding or subtracting a percentage.
Why an Online Percentage Calculator Is So Useful
Percentages show up everywhere: shopping discounts, tax, grades, savings goals, salary raises, business reports, and investment performance. A good online percentage calculator saves time and removes math errors by giving instant results for common percentage formulas.
Instead of searching for a different tool each time, this page combines the most-used percentage calculations in one place. You can find percent values, reverse percentages, percentage increase and decrease, and adjusted totals after adding or subtracting a percent.
Common Percentage Problems This Tool Solves
1) Find a percentage of a number
Use this when you need results like: “What is 15% of 240?” The formula is (X ÷ 100) × Y.
2) Find what percent one number is of another
Use this for questions such as: “30 is what percent of 120?” The formula is (X ÷ Y) × 100.
3) Calculate percentage increase or decrease
Perfect for tracking growth and decline in revenue, website traffic, body weight, or prices. The formula is ((New − Old) ÷ Old) × 100.
4) Add or subtract a percentage
Useful for markups, markdowns, tips, tax-inclusive pricing, and budget adjustments. Multiply by (1 + p/100) to add, or (1 − p/100) to subtract.
Real-World Examples
- Discount percentage calculator: A $80 item with 25% off gives a $20 discount and a $60 final price.
- Sales tax percentage: Add 8.5% tax to a $120 purchase to estimate total checkout cost.
- Tip percentage calculator: Add 18% or 20% tip to a restaurant bill in seconds.
- Grade percentage calculator: Find your score percentage from points earned versus total points.
- Percentage change calculator: Compare this month’s sales to last month’s and measure growth.
Tips for Accurate Percentage Calculations
- Double-check which value is the base (the “whole”).
- Use the same units before calculating percentages (dollars with dollars, units with units).
- For percentage change, avoid dividing by zero. If the original value is zero, percent change is not defined in the usual way.
- Round only at the end if you need high precision.
Percentage vs Percentage Points
These are often confused. If a rate rises from 10% to 12%, that is:
- +2 percentage points (12% − 10%)
- +20% relative increase ((12 − 10) ÷ 10 × 100)
Knowing the difference helps when reading finance, economics, and analytics reports.
Quick FAQ
How do I calculate 20% of 150?
Multiply 150 by 0.20. The result is 30.
How do I find the original value before a discount?
If the final price is known, divide by (1 − discount%). Example: $80 after a 20% discount means original price was $100.
Can I use this calculator for business and finance?
Yes. It works for markup calculations, margin checks, KPI reporting, and quick performance comparisons.
Final Thoughts
This online percentage calculator is built for speed, clarity, and everyday use. Whether you need a simple percent-of-number result or a detailed percentage increase/decrease calculation, you can get the answer instantly and confidently. Bookmark this page if you regularly work with discounts, taxes, grades, financial planning, or data analysis.