Percentage of a Number Calculator
Why use this calculator
"What is X% of Y" is one of the most common small math tasks — tips, discounts, sales tax, commission, splitting a bill — and doing it in your head is easy to get wrong once decimals are involved. This tool gives you the exact answer instantly.
Enter both values to see the result.
How it works
The formula is:
result = (percentage / 100) × number
For example, to find 7.5% sales tax on a $42.00 purchase: (7.5 / 100) × 42 = $3.15 in tax.
Worked examples
- Tip on a restaurant bill: 20% of $58.40 = $11.68 tip.
- Discount on a purchase: 30% of $120 = $36 off, so the sale price is $120 − $36 = $84.
- Commission: 5% of $12,000 in sales = $600 commission.
Frequently asked questions
- How do I calculate X% of a number?
- Multiply the number by the percentage, then divide by 100. For example, 15% of 80 is 15 × 80 / 100 = 12.
- How do I use this for a tip calculation?
- Enter the tip percentage you want to leave (e.g. 18) in the first field, and your bill total in the second. The result is the tip amount — add it to the bill for the total.
- Can I use this for a percentage discount?
- Yes — enter the discount percentage and the original price. The result is the amount taken off; subtract it from the original price to get the sale price.
- What if I enter a percentage over 100?
- That's valid — it just means the result is larger than the original number. For example, 150% of 40 is 60, since it's 1.5 times the original value.