About Percentage Calculator
Calculate percentages six ways: X% of Y, percentage change, increase, decrease, and more. Free, no sign-up required.
How to use
- Use the first row 'What is X% of Y' for finding a portion of a total. Enter the percentage on the left and the base number on the right. Example use: calculating a 15% tip on a $48 restaurant bill, finding 13% HST on a $250 invoice, or computing a 20% commission on $1,500 in sales.
- Use the second row 'X is what % of Y' to find what fraction one number represents of another. Enter the part first, then the whole. Example: 35 students passed out of 42 — what is the pass rate? 35 is 83.33% of 42. This mode is ideal for grade calculations, attendance rates, and conversion metrics.
- Use the third row 'X is Y% of what' for reverse calculations when you know the result and the percentage. Example: a deposit of $5,000 represents 20% of the total purchase price — what is the total price? Answer: $25,000. This is the standard formula for deposit and down-payment math.
- Use the percentage change row to track increases or decreases between two values. Enter the old value first, then the new value. The result is positive for increases and negative for decreases. Use this for stock returns, year-over-year revenue changes, or measuring weight loss progress.
- Use the increase and decrease rows for one-step calculations on adjusted values. 'Increase $80 by 25%' returns $100 directly (no separate addition). 'Decrease $200 by 30%' returns $140. These two rows handle markup pricing, discount math, and tax-inclusive totals in a single step.
- Watch out for percentage change traps: a 50% increase followed by a 50% decrease does not return you to the original. $100 + 50% = $150, then $150 - 50% = $75 (a net 25% loss). Sequential percentages multiply, they do not add. Two 10% discounts on a $100 item give $81, not $80.
Examples
Restaurant tip in Ontario
A $48 dinner bill in Ontario. HST at 13%: $48 x 0.13 = $6.24, total with tax $54.24. Tip 18% on the pre-tax amount: $48 x 0.18 = $8.64. Final total: $54.24 + $8.64 = $62.88. Quick check: round to $50 base, 20% tip is $10 — close to the precise answer.
Stock return calculation
Bought 100 shares at $42 each ($4,200 total). Sold 8 months later at $51 per share ($5,100 total). Percentage gain: ((5,100 - 4,200) / 4,200) x 100 = 21.43%. Annualized return (8 months scaled to 12): 21.43% x (12/8) = 32.14% — a strong year if sustained.
Double discount on a sweater
Original price $120. First discount 30% off: $120 x 0.70 = $84. Extra 20% off at checkout: $84 x 0.80 = $67.20. Total saved: $52.80, or 44% off the original — not 50% (which would have been $60). Sequential discounts always combine to less than the simple sum.
Frequently asked questions
How do I calculate percentage of a total?
Multiply the percentage (as a decimal) by the total. 15% of $48 = 0.15 x 48 = $7.20. 13% HST on a $250 invoice = 0.13 x 250 = $32.50. To find the percentage when you have the part and whole, divide the part by the whole and multiply by 100. 7.20 is what % of 48? (7.20 / 48) x 100 = 15%. The first row of this calculator does the multiplication directly without converting to decimal yourself, so you can enter percentages as whole numbers (15, not 0.15).
What is the formula for percentage change?
Percentage change = ((new value - old value) / old value) x 100. From $80 to $100: ((100 - 80) / 80) x 100 = 25% increase. From $100 to $80: ((80 - 100) / 100) x 100 = -20% decrease. The result is asymmetric: a price doubling is +100%, but a price halving is -50%. To restore a value after a percentage drop, the increase needed is greater than the original drop. A 20% loss requires a 25% gain to break even (0.80 x 1.25 = 1.00). A 50% loss requires a 100% gain to break even.
What is the difference between percentage change and percentage points?
Percentage change is relative — comparing the new value to the old value. Going from a 5% interest rate to a 7% interest rate is a 40% relative increase ((7-5)/5 x 100) but a 2 percentage point increase in absolute terms. News headlines often confuse these: 'unemployment rose 50%' could mean from 4% to 6% (2 percentage points, 50% relative) or from 4% to 4.02% (statistically meaningless). When discussing rates, always clarify which measure you mean. Percentage points are the safer, less misleading measure for rate comparisons.
How do tips and tax work in Canada?
Standard restaurant tips in Canada are 15-18% on the pre-tax subtotal, with 20% becoming common for excellent service in major cities. Some calculate tips on the post-tax total (which slightly increases the tip) — both are acceptable, with post-tax tipping more common in Quebec. HST/GST varies by province: 13% in Ontario, 15% in Atlantic provinces, 5% GST plus 7% PST in BC (combined 12%), 5% GST in Alberta. A $50 meal in Ontario: $50 + 13% HST = $56.50. Tip 18% on $50 (pre-tax) = $9. Total: $65.50. Tip 18% on $56.50 (post-tax) = $10.17. Total: $66.67.
How do compound percentage changes work?
Sequential percentages multiply, not add. Two 10% discounts on a $100 item: first discount gives $90, second discount on $90 gives $81. Not $80 (which would be a single 20% discount). The combined effect is 1 - (0.90 x 0.90) = 0.19 = 19% off, not 20%. For three discounts of 10%: 1 - (0.90)^3 = 1 - 0.729 = 27.1% off, not 30%. Compound increases work the same way: 10% inflation per year for 5 years compounds to 1.10^5 = 1.611, a 61.1% total increase, not 50%. This is why 'rule of 72' approximates how long money takes to double at a given growth rate.
What is the difference between margin and markup?
Markup is profit as a percentage of cost. Margin is profit as a percentage of selling price. A widget costs $60 and sells for $100. Profit = $40. Markup = 40 / 60 = 66.67%. Margin = 40 / 100 = 40%. Markup is always higher than margin for the same item. Retailers think in markup (how much above cost to set the price), while accountants and investors think in margin (how much of revenue is profit). Common conversion: 50% markup = 33% margin. 100% markup = 50% margin. 200% markup = 67% margin. The
Margin Calculator handles this conversion directly with cost, price, and margin/markup all visible at once.
How do I calculate a discount price quickly?
Decrease X by Y%: multiply the original price by (1 - discount/100). $80 with 25% off: $80 x 0.75 = $60. $150 with 30% off: $150 x 0.70 = $105. For mental math, compute 10% (move decimal one place) and scale: 10% of $80 is $8, so 25% is $20, so $80 - $20 = $60. For double discounts (e.g., 'extra 20% off already-discounted items'), apply each discount separately. 30% off then extra 20% off on $100: $100 x 0.70 x 0.80 = $56, which is a 44% total discount, not 50%.
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