% Percentage Calculator

What This Calculator Does

This calculator handles the three percentage questions that come up most in everyday life: what is X percent of a number, what percent one number is of another, and the percentage change between two numbers. Pick the question you have, enter your values, and it gives you the answer instantly. It covers the calculations behind tips, discounts, test scores, statistics, and countless other situations where percentages appear.

Percentages are simple in principle but easy to fumble in practice, especially when you are not sure which calculation you actually need. This tool removes that uncertainty by separating the common questions clearly, so you always apply the right one and get a reliable answer without second-guessing the math.

The Three Core Percentage Calculations

Finding a percentage of a number is the most common: 20% of 150 is found by multiplying 150 by 0.20, giving 30. This is the math behind tips, discounts, and tax. Finding what percent one number is of another answers questions like “45 out of 60 is what percent?” — you divide 45 by 60 and multiply by 100, getting 75%. This is how test scores and proportions work.

The third, percentage change, measures how much a value grew or shrank between two points: the difference divided by the original value, as a percent. Going from 80 to 100 is a 25% increase, because the change of 20 divided by the original 80 is 0.25. The key with this one is always dividing by the starting value, not the ending value — a distinction this calculator handles for you so you never get it backwards.

Quick Tips

• To find a percentage of a number, convert the percent to a decimal and multiply — 20% becomes 0.20.
• For “what percent is X of Y,” divide X by Y and multiply by 100.
• For percentage change, always divide by the original (starting) value, never the new one.
• A quick check: 10% of any number is just that number with the decimal moved one place left.

Frequently Asked Questions

How do I find a percentage of a number?

Convert the percentage to a decimal and multiply. To find 20% of 150, multiply 150 by 0.20 to get 30. This calculator does it instantly for any values.

How do I find what percent one number is of another?

Divide the first number by the second and multiply by 100. For 45 out of 60, that is 45 divided by 60, times 100, which equals 75%.

How do I calculate percentage change?

Subtract the original value from the new value, divide by the original value, and multiply by 100. Always divide by the starting value — dividing by the new value gives the wrong answer.

What is a quick way to find 10% of something?

Move the decimal point one place to the left. Ten percent of 250 is 25. From there you can find other percentages — 20% is double that, 5% is half.