Percentage Calculator: How to Calculate Any Percentage Instantly

Type 1 — What is X% of a number? Formula: result = (X/100) × number. Example: What is 18% of $47.50 (restaurant tip)? 0.18 × 47.50 = $8.55. For quick mental math, break it down: 10% of $47.50 = $4.75, then 8% ≈ $3.80, total ≈ $8.55.

Type 2 — X is what percent of Y? Formula: percent = (X/Y) × 100. Example: You scored 43 out of 50 on a test — what percent? (43/50) × 100 = 86%. Or you saved $12 on a $60 item — the discount was (12/60) × 100 = 20%.

Type 3 — Percentage change between two values. Formula: change = ((new − old) / old) × 100. A stock rose from $45 to $52: ((52 − 45) / 45) × 100 = 15.6% increase. A salary dropped from $75,000 to $68,000: ((68,000 − 75,000) / 75,000) × 100 = −9.3% decrease.

Percent increase vs. percent of: these are different calculations. A 20% increase on $100 gives $120, not 20% of $120 ($24). When something 'increases by 20%,' you multiply by 1.20. When something 'is 20% of' another number, you multiply the other number by 0.20.

Percentage point vs. percentage: if a tax rate goes from 20% to 25%, it increased by 5 percentage points — but it increased by 25% (5/20 × 100). Mixing these up is a common error in financial and political reporting. Always clarify which you mean.

Discount stacking: two 10% discounts are NOT the same as a 20% discount. After the first 10% discount, the new price is 90% of original. The second 10% applies to that new price: 90% × 90% = 81% of original — a 19% total discount, not 20%.

Tips: 15% tip = move the decimal left one place (10%), then add half. On $43.50: $4.35 + $2.18 = $6.53. For 20%, move decimal left one place and double: $4.35 × 2 = $8.70. For 18%, use the percentage calculator for precision.

Sales and discounts: to find the sale price after X% off, multiply by (1 − X/100). A 30% discount on $79.99: $79.99 × 0.70 = $55.99. To find original price from discounted price: sale price / (1 − discount%). $55.99 / 0.70 = $79.99.

Interest rates: a 6.5% APR on a $10,000 credit card balance costs $650 per year in interest — but credit cards compound monthly, so the effective rate (APY) is slightly higher. Use our percentage calculator to quickly compare rates, tax savings, or any return on investment scenario.