Unit Converter

To calculate a percentage of a number manually, convert the percentage to a decimal by dividing it by 100, then multiply by the number. For example, to find 18% of 250: 18 ÷ 100 = 0.18, then 0.18 × 250 = 45. So 18% of 250 is 45. If you're calculating a discount, subtract the result from the original price: $250 – $45 = $205. For a tip, add the result: a 20% tip on a $60 bill is 0.20 × 60 = $12, making the total $72. For a sales tax of 7.25% on a $120 purchase, 0.0725 × 120 = $8.70, so you pay $128.70. This unit converter does that multiplication for you in one step. If you need to convert between units like inches and centimeters after finding a percentage, use the length-converter. The same math applies whether you're working with dollars, meters, or kilograms.

Percentage points measure the arithmetic difference between two percentages, while percentage measures relative change. If an interest rate rises from 4% to 6%, that's a 2 percentage point increase, but it's a 50% relative increase (because 2 ÷ 4 = 0.5). Confusing the two can lead to misreading financial news. For example, if a savings account rate goes from 1.5% to 2.25%, that's a 0.75 percentage point increase, which is a 50% relative increase. If you're comparing two rates, always ask whether the change is in points or percent. This calculator helps you find a percentage of a value, not the difference between two percentages. To find the percentage difference between two numbers, subtract the smaller from the larger, divide by the original, and multiply by 100. For instance, 30 to 45 is a 50% increase: (45 – 30) ÷ 30 × 100 = 50. If you're working with currency conversions, the currency-converter can help you apply those percentages to different currencies.

To find the original price before a discount, divide the sale price by (1 minus the discount rate as a decimal). Suppose a jacket is on sale for $68 after a 15% discount. The discount rate as a decimal is 0.15, so 1 – 0.15 = 0.85. Divide $68 by 0.85 to get $80. So the original price was $80, and you saved $12. Alternatively, if you know the discount amount and the percentage, divide the discount amount by the percentage and multiply by 100. For example, if you saved $12 and the discount was 15%, then $12 ÷ 15 × 100 = $80. This unit converter gives you the discount amount when you enter the original price and percentage. For a $200 item at 25% off, the result is $50, so the sale price is $150. If you need to convert that price to another currency, the currency-converter can handle the exchange rate. Always double-check whether the discount is applied before or after tax, as that changes the final price.

A common mistake is adding or subtracting the percentage from the number without converting it to a decimal. For example, to find a 20% increase on 150, some people incorrectly do 150 + 20 = 170 instead of 150 + (0.20 × 150) = 180. Another mistake is reversing the base and the percentage. If you need 15% of 80, the answer is 12, but if you accidentally calculate 80% of 15, you also get 12—this symmetry only works when the product is the same, which is rare. A more serious error is confusing percentage increase with percentage points. If a fee goes from 2% to 3%, that's a 1 percentage point increase, but a 50% relative increase. Also, forgetting to divide by 100 when using a calculator leads to results that are 100 times too large. For instance, 7% of 300 is 21, not 2100. This unit converter automatically divides by 100, so you just enter 7 and 300. For mortgage-related percentage calculations, like interest on a $400,000 loan at 6.5%, the mortgage-calculator can break down monthly payments.

To calculate a tip or sales tax quickly, multiply the bill by the percentage as a decimal. For a 20% tip on a $45 meal: 0.20 × 45 = $9, so the total is $54. For a 15% tip, 0.15 × 45 = $6.75, total $51.75. For sales tax of 8.875% on a $120 purchase: 0.08875 × 120 = $10.65, total $130.65. A quick mental shortcut for a 20% tip is to move the decimal one place to the left to get 10% ($4.50), then double it ($9). For 15%, take 10% ($4.50) and add half of that ($2.25) to get $6.75. For sales tax, you can estimate by rounding the rate: 8.875% is close to 9%, so 9% of $120 is $10.80. This unit converter gives you the exact amount when you enter the bill and the percentage. If you're traveling and need to convert the total to another currency, use the currency-converter. For weight-based taxes or shipping, the weight-converter can help you convert pounds to kilograms.

Yes, but you need one extra step. This unit converter gives you the portion—the amount of the increase or decrease. To find the new total, add or subtract that portion from the original value. For example, if your rent increases by 6% from $1,500, enter 1500 and 6 to get 90. Then add 90 to 1500 for a new rent of $1,590. If your phone bill decreases by 12% from $80, enter 80 and 12 to get 9.60, then subtract 9.60 from 80 for a new bill of $70.40. To find the percentage change between two numbers, use the formula: (new – old) ÷ old × 100. If a stock goes from $50 to $65, the change is (65 – 50) ÷ 50 × 100 = 30% increase. If it drops to $40, the change is (40 – 50) ÷ 50 × 100 = –20% decrease. This calculator handles the portion part; you handle the addition or subtraction. For loan-related percentage changes, like adjusting a mortgage rate, the mortgage-calculator can show the impact on monthly payments. For unit conversions after calculating, try the length-converter or weight-converter.