Percentage Calculator: How to Calculate Discounts, Sales Tax, and Tips in Seconds

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Percentages are everywhere in daily life: store discounts, restaurant tips, sales tax, loan interest, exam scores, and investment returns. Whether you are shopping during a sale, dining out with friends, or calculating your tax refund, knowing how to calculate percentages quickly saves time and helps you make better financial decisions.

Use the Percentage Calculator on Today Calculator for instant results — no math required.

Everyday Percentage Scenarios

ScenarioExampleCalculationResult
Discount$80 jacket at 25% off80 × 0.25 = 20$60 (save $20)
Restaurant tip$65 dinner, 18% tip65 × 0.18 = 11.70$76.70 total
Sales tax$200 item, 8.5% tax200 × 0.085 = 17$217 total
Loan interest$10,000 at 6% APR10000 × 0.06 = 600$600/year interest
Grade calculation45 out of 50 on test45 ÷ 50 × 100 = 9090% (A-)
Investment gain$1,000 → $1,250(1250−1000)÷1000×10025% gain

Calculate any percentage scenario instantly with our Percentage Calculator.

The Three Percentages You Need to Know

Finding the Percentage of a Number

Formula: (Percentage ÷ 100) × Total = Result
Example: 15% of $240 = (15 ÷ 100) × 240 = 0.15 × 240 = $36

Finding What Percentage One Number Is of Another

Formula: (Part ÷ Whole) × 100 = Percentage
Example: You scored 38 out of 40. (38 ÷ 40) × 100 = 95%

Finding the Original Number Before a Percentage Change

Formula: Result ÷ (1 + Percentage/100) = Original
Example: You paid $118.80 including 8% tax. $118.80 ÷ 1.08 = $110.00 original price

Quick Mental Math Tricks for Percentages

  • 10%: Divide by 10 (e.g., 10% of $85 = $8.50)
  • 5%: Take 10% and halve it (10% of $85 = $8.50 → 5% = $4.25)
  • 1%: Divide by 100 (1% of $85 = $0.85)
  • 15%: Add 10% + 5% ($8.50 + $4.25 = $12.75)
  • 20%: Double 10% ($8.50 × 2 = $17.00)

For any percentage calculation, use the Percentage Calculator for error-free results.

Common Percentage Mistakes

  • “50% + 25% = 75%” — If an item is 50% off, then an additional 25% off means you pay 50% of the original, then 75% of that. 0.50 × 0.75 = 0.375. You pay 37.5% of the original, not 25%.
  • Confusing percentage points with percent — A rate increase from 4% to 6% is a 2 percentage point increase, but a 50% increase in the rate.
  • Applying a discount twice — 20% off then 10% off ≠ 30% off. It’s 0.80 × 0.90 = 0.72 = 28% total discount.

Use the Percentage Calculator to avoid these common errors.

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