I Built This to Make Percentages
Actually Make Sense
I've spent years helping people understand percentages—from calculating tips to figuring out sales discounts. This calculator handles all the common scenarios you actually need in real life.
1What is X% of Y?
Example: "What's 15% of $200?" (Like calculating a tip)
2X is what % of Y?
Example: "30 is what % of 120?" (Like finding what % you scored on a test)
3Percentage Change
Example: "From 100 to 150" (Like calculating price increases or decreases)
Percentage Calculator in 3 Simple Steps
Pick Your Question
Choose which type of percentage problem you're solving. Most people need Calculator #1 (What is X% of Y?) for tips, discounts, and taxes.
Enter Your Numbers
Type in your values. The calculator updates instantly—no need to hit 'Calculate.' I've made it as simple as possible.
Get Your Answer
Your result appears immediately. Use it for whatever you need—shopping, budgeting, homework, or just satisfying your curiosity.
Real-World Examples I Use Every Day
Percentages aren't just for math class. Here's where I actually use them in real life.
Restaurant Tips
Example: Bill is $85. What's a 20% tip?
Solution: Use Calculator #1: 20% of 85 = $17
Pro tip: For 20%, just move the decimal left one place and double it. $85 → $8.50 → $17.
Sales & Discounts
Example: Shirt is $60, 30% off. Final price?
Solution: 30% of 60 = $18 off. Final price: $60 - $18 = $42
Or use Calculator #3: From $60 to what price is -30%? Reverse engineer it.
Test Scores
Example: Got 42 out of 50 questions right. What's my %?
Solution: Use Calculator #2: 42 is what % of 50? = 84%
This works for any 'X out of Y' scenario—games, surveys, completion rates.
Salary Raises
Example: Salary went from $50k to $55k. What % raise?
Solution: Use Calculator #3: From 50000 to 55000 = +10%
Always calculate % change from the original number, not the new one.
The Formulas Demystified
I know formulas look scary. Let me break them down in plain English.
Formula #1: What is X% of Y?
(X ÷ 100) × Y = Result
Or in plain English: "Turn the % into a decimal, then multiply"
Example: What is 15% of 200?
• Step 1: 15 ÷ 100 = 0.15
• Step 2: 0.15 × 200 = 30
• Answer: 30
Formula #2: X is what % of Y?
(X ÷ Y) × 100 = Result%
Or: "Divide the part by the whole, then multiply by 100"
Example: 30 is what % of 120?
• Step 1: 30 ÷ 120 = 0.25
• Step 2: 0.25 × 100 = 25
• Answer: 25%
Formula #3: Percentage Change
((New - Old) ÷ Old) × 100 = Change%
Or: "Find the difference, divide by the original, multiply by 100"
Example: From 100 to 150
• Step 1: 150 - 100 = 50 (the change)
• Step 2: 50 ÷ 100 = 0.5
• Step 3: 0.5 × 100 = 50
• Answer: +50% increase
Mental Math Tricks I Actually Use
You don't always need a calculator. Here are shortcuts I use when I'm out and about.
10% of anything
Method: Move the decimal point left one place
10% of $47.50 = $4.75
20% (for tips)
Method: Find 10%, then double it
10% of $85 = $8.50, so 20% = $17
15% (for tips)
Method: Find 10%, then add half of that
10% of $60 = $6, half is $3, so 15% = $9
50% of anything
Method: Just divide by 2
50% of $124 = $62
25% of anything
Method: Divide by 4
25% of $80 = $20
1% of anything
Method: Move decimal left two places
1% of $350 = $3.50
Percentage FAQs: The Questions I Get All the Time
Percentage is a fraction of 100 (like 75% means 75 out of 100). Percentile is your rank compared to others (75th percentile means you scored better than 75% of people). Completely different concepts that people mix up all the time.
Absolutely! If something doubles, that's a 100% increase. If it triples, that's a 200% increase. Percentages over 100% just mean 'more than the original amount.' It's common in growth rates, returns on investment, and price increases.
Because they're based on different starting points. Example: If a stock goes up 50% then down 50%, you don't break even—you lose 25%. The 50% down is calculated from the higher price, not the original. Always calculate each percentage from its own base.
For 20%: Move the decimal left one place, then double it. For 15%: Find 10% (move decimal left), then add half of that. For 18%: Find 10%, double it (20%), then subtract 10% ÷ 5 (2%). Or just use this calculator—that's why I built it.
If something is 30% off and costs $70, divide by 0.7 (which is 100% - 30% = 70%). So $70 ÷ 0.7 = $100 original price. General formula: Final Price ÷ (1 - Discount%) = Original Price.
If interest rates go from 5% to 8%, that's a 3 percentage point increase, but a 60% increase. Percentage points = simple subtraction (8 - 5 = 3). Percent increase = relative change ((8-5)/5 × 100 = 60%). News often mixes these up.
Because percentages sound bigger. '50% more' sounds better than '6 extra ounces.' It's marketing psychology. Always convert to actual numbers to see if it's a good deal. Sometimes '50% more' is only a few cents of actual value.
Yes, but you multiply the decimals, not add the percentages. Example: 20% off, then another 10% off isn't 30% off total. It's: 0.8 × 0.9 = 0.72, so you pay 72% of original price = 28% off total. Stores love this trick.
Nothing. 'Percent' is American English, 'per cent' is British English. Both mean 'per hundred' (from Latin 'per centum'). Use whichever spelling your country prefers. The symbol % works everywhere.
Use Calculator #2 above. Formula: (Part ÷ Whole) × 100. Example: 'What % is 30 of 120?' → (30 ÷ 120) × 100 = 25%. This is probably the most common percentage calculation in real life.
Percentages Don't Have to Be Confusing
Whether you're calculating tips, figuring out discounts, or just trying to understand your test score, this calculator has you covered. Bookmark it—you'll use it more than you think.