Percentage Calculator
This free percentage calculator computes a number of values involving percentages, including the percentage difference between two given values.
How to Use the Percentage Calculator
Choose a mode such as percent of a number, what percent one value is of another, or percent increase/decrease. Enter values and calculate to get quick results for pricing, finance, grade analysis, and growth comparisons.
Core Percentage Modes
Most practical tasks use three modes: percent of a value, ratio to percent conversion, and percent change between two values.
Applied Use Cases
Percentage math is central to discounts, taxes, analytics dashboards, budgeting, and business reporting.
Common Pitfalls
Choosing the wrong base value and mishandling zero baselines are the two most common percent-calculation errors.
Interpreting Large Changes
A 100% increase means doubling, while a 50% decrease is not reversed by a 50% increase. Direction and base both matter.
Accuracy and Rounding
Keep higher precision during intermediate steps and round only at the final display stage for reliable outputs.
Frequently Asked Questions
How do I calculate a 20% discount?+
Multiply price by 0.20 to find discount amount, then subtract it from the original price.
How do I find what percent 45 is of 120?+
Divide 45 by 120 and multiply by 100. That gives 37.5%.
What is percent increase formula?+
Use ((new - old) / old) * 100. Positive values indicate increase.
What is percent decrease formula?+
Use ((old - new) / old) * 100 or allow the standard change formula to return a negative value for decreases.
Can percentage change exceed 100%?+
Yes. If a value more than doubles from the original, the increase is above 100%.
Why is percent change undefined sometimes?+
If the original value is zero, percent change is not defined because division by zero is invalid.
What is the difference between markup and margin?+
Markup is based on cost, margin is based on selling price. They are related but not identical.
How is percent used in finance?+
Percent is used for returns, discount rates, tax rates, interest rates, and allocation weights.
How do I avoid percentage mistakes?+
Convert percentages to decimals carefully and verify base value selection before finalizing.
Should I round percentage outputs?+
Round for display, but keep more precision internally when small differences matter.
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