What is 15% of 200?
How to Use the Percentage Calculator
Switch between three modes: “Percentage of” finds what X% of Y is; “% Change” calculates the increase/decrease from one number to another; “% Difference” finds the relative difference between two numbers. Enter your values and click Calculate for an instant result.
Why Percentages Matter
Percentages are used everywhere in daily life — from calculating tips and discounts to understanding interest rates, tax rates, investment returns, and statistical data. Mastering percentage calculations helps you make better financial decisions.
Common Percentage Uses
- Sales & Discounts: “30% off” means you pay 70% of the original price
- Taxes: Sales tax, income tax brackets are expressed as percentages
- Investments: Annual percentage yield (APY), stock returns
- Statistics: Survey results, population growth, probability
- Grades: Test scores, final grade calculations
How to Calculate Percentages Manually
To find X% of Y: multiply Y by X and divide by 100. For percentage change: ((New – Original) / Original) x 100. For percentage difference: (|A – B| / ((A + B) / 2)) x 100. Our calculator handles all three formulas instantly.
Percentage Calculator: Complete Guide to Percentages
Percentages are everywhere in daily life – sales, taxes, tips, interest rates, statistics, and grades. Understanding how percentages work helps you make better financial decisions and interpret data more accurately.
Percentage in Daily Life
| Scenario | Calculation | Example |
|---|---|---|
| Sales tax | Price x Tax Rate | $50 at 8% = $4 tax |
| Discount | Original x Discount% | $80 at 25% off = $20 savings |
| Commission | Sales x Commission% | $10,000 at 3% = $300 |
| Grade | Score / Total x 100 | 45/50 = 90% (A-) |
| Tip | Bill x Tip% | $40 at 18% = $7.20 |
How to Calculate Percentages Mentally
- 10%: Divide by 10. $150 -> $15
- 5%: Half of 10%. $150 -> $7.50
- 15%: 10% + 5%. $150 -> $22.50
- 20%: 10% x 2. $150 -> $30
- 25%: Half of half. $150 -> $37.50
- 50%: Divide by 2. $150 -> $75
Percentage Change: Increase and Decrease
To calculate percentage increase: (New – Original) / Original x 100. If a stock goes from $50 to $60: (10/50) x 100 = 20% increase. For decrease: (Original – New) / Original x 100. $60 drops to $45: (15/60) x 100 = 25% decrease.
Compound Percentages: The Power of Growth
If an investment grows 10% per year, it doubles in about 7.2 years (Rule of 72). A 7% annual return doubles in 10.3 years. Over 30 years, $10,000 at 7% grows to $76,123. At 10%, it grows to $174,494. At 15%, it becomes $662,118. The percentage rate makes a massive difference over time.
Percentage Points vs Percent Change
A common confusion: if an interest rate rises from 5% to 6%, that is a 1 percentage point increase but a 20% increase in the rate. Always clarify which is being referenced in financial discussions. A stock dropping from 50% to 40% is a 10 percentage point drop, or a 20% relative decline.
Common Percentage Mistakes to Avoid
- Adding percentages directly: 10% + 20% of the same base = 10% of base + 20% of base = 30% of base
- But a 10% discount followed by a 20% discount is NOT 30% off – the second discount applies to the already-discounted price
- $100 with 10% off = $90, then 20% off = $72 total, which is 28% off total
- A 50% increase followed by a 50% decrease does NOT return to the original – $100 -> $150 -> $75 (25% loss)