Percentage Calculator
Calculate percentages in three ways: X% of Y, X is what % of Y, and percentage change between two values.
How to Use
- 1
Choose a mode
Select from: X% of Y, X is what % of Y, or % change.
- 2
Enter values
Fill in the two input fields.
- 3
Calculate
Get the result instantly.
How It Works
Percentage problems usually fall into one of three shapes, and mixing them up is the most common source of errors. This tool separates them into three explicit modes so you calculate the right thing instead of guessing which formula applies.
Mode 1 — X% of Y
Formula: (X ÷ 100) × Y. Example: 15% of 240 = (15 ÷ 100) × 240 = 36. Used for tips, discounts, commissions, and tax on a known amount.
Mode 2 — X is what % of Y
Formula: (X ÷ Y) × 100. Example: 45 is what % of 180? (45 ÷ 180) × 100 = 25%. Used for finding a score's percentage, a portion of a total, or a completion rate.
Mode 3 — Percentage change between two values
Formula: ((New − Old) ÷ |Old|) × 100. Example: price moves from 80 to 92: ((92 − 80) ÷ 80) × 100 = 15% increase. A negative result means a decrease. This is the mode people most often get wrong by dividing by the new value instead of the old one.
Examples
Restaurant tip
Bill is ₹1,240 and you want to leave 18%: (18 ÷ 100) × 1,240 = ₹223.20 tip, ₹1,463.20 total.
Exam score
You scored 68 out of 85: (68 ÷ 85) × 100 = 80%.
Salary hike
Salary goes from ₹45,000 to ₹52,000/month: ((52,000 − 45,000) ÷ 45,000) × 100 ≈ 15.56% increase.
Common Use Cases
- Calculating discounts, tips, taxes, or commissions on a bill or invoice
- Converting test/exam scores into percentages
- Measuring salary hikes, price changes, or year-over-year growth
- Working backward from a final price to find the original amount (using the change formula in reverse)
Tips
- "Percentage change" and "percentage points" are not the same thing — if interest rates go from 5% to 7%, that's a 2 percentage-point rise but a 40% relative increase. Be clear about which one you mean.
- Always divide by the original (old) value in a percentage-change calculation, not the new one — dividing by the new value is the single most common percentage mistake.
- For successive percentage changes (e.g. +10% then −10%), the result is not 0% — it's a net −1%, because the second percentage applies to a different base amount.
Frequently Asked Questions
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