Percentage Calculator
Percentage Calculator is a free online tool to calculate percentages.
How to use this percentage calculator
Each row answers a different everyday question, and all three calculations run in your browser — nothing you type is sent to a server. Type whole numbers or decimals, then select Calculate or press Enter.
- What is X% of Y? Use this for discounts, tips, sales tax, GST, commissions and interest amounts.
- X is what percent of Y? Use this to convert a score, a share of a budget, or a portion of a total into a percentage.
- Percentage increase or decrease from X to Y? Use this to compare two figures over time, such as last year's revenue against this year's. A negative result is a decrease.
The three percentage formulas
Percentages are just fractions of 100, so every calculation on this page comes from one of three simple formulas.
- Percentage of a number: (percentage ÷ 100) × number. So 15% of 240 = (15 ÷ 100) × 240 = 36.
- One number as a percentage of another: (part ÷ whole) × 100. So 45 out of 180 = (45 ÷ 180) × 100 = 25%.
- Percentage change: ((new − old) ÷ old) × 100. So a move from 80 to 92 = ((92 − 80) ÷ 80) × 100 = 15%.
Worked examples
Sales tax and GST
Australia applies a 10% goods and services tax (GST) to most taxable supplies, so a AUD 480 invoice attracts AUD 48 in GST — enter 10 and 480 in the first row. In the United States sales tax is set by state and local jurisdictions rather than nationally, so use the combined rate that applies where the sale occurs: at a 8.5% combined rate, a USD 480 purchase adds USD 40.80.
Tips and service charges
Tipping is customary in US restaurants, where 18–20% of the pre-tax bill is a common range. On a USD 76 bill, 20% is USD 15.20. Tipping is not expected in the same way in Australia, where award wages apply.
Comparing two figures
If a household's weekly grocery spend rises from AUD 210 to AUD 231, the third row returns 10% — an increase. If it falls back to AUD 210, the change from 231 is about −9.09%, because percentage change is always measured against the starting value. That asymmetry is why a 50% fall requires a 100% rise to recover.
Percent versus percentage points
When a central bank moves a policy rate from 4.00% to 4.25%, that is a rise of 0.25 percentage points, not 0.25%. In relative terms it is a 6.25% increase. Interest rates, unemployment rates and poll numbers are normally reported in percentage points, so check which measure a figure refers to before comparing it with another.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. The first row of the calculator does this for you.
How do I find what percentage one number is of another?
Divide the first number by the second and multiply by 100. The second row handles this, and it will flag an error if the second number is zero, because dividing by zero is undefined.
Can I calculate a percentage decrease?
Yes. Enter the original value first and the new value second in the third row. A negative result means the value fell.
Does the calculator accept decimals and negative numbers?
Yes to both. Results are rounded to six decimal places, which is well beyond the precision most everyday calculations need.
This tool provides general mathematical calculations only. It is not financial, tax or accounting advice. Tax rates, thresholds and rounding rules differ between Australia and the United States and between individual states, so confirm the applicable rate with the relevant authority or a qualified adviser before relying on a figure.