Percentages are behind most money decisions in a business: discounts, margins, price increases, tax, conversion rates and growth. The questions all look alike, which is why they get mixed up. This calculator gives each common question its own box, so you type the numbers in the sentence that matches what you want to know and read the answer and the formula straight away.
All eight boxes are live on the page at once, and each one shows the formula with your numbers so you can check the math or repeat it in a spreadsheet. Nothing leaves your browser.
How to use the percentage calculator
- Find the box whose sentence matches your question, for example What is __% of __? or From __ to __ for a percent change.
- Type your two numbers. The result appears immediately, with the formula underneath.
- In Add or subtract a percentage and Original number before a change, choose increase or decrease from the drop-down.
- Click Copy to copy a result without commas, ready to paste into a spreadsheet.
Results are rounded to 4 decimal places. Negative numbers work in every box.
The percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y x X / 100 | 20% of 150 = 30 |
| X is what percent of Y? | X / Y x 100 | 30 of 150 = 20% |
| X is P% of what? | X / (P / 100) | 30 is 20% of 150 |
| Percent change from A to B | (B - A) / A x 100 | 80 to 100 = +25% |
| Increase Y by P% | Y x (1 + P / 100) | 80 + 25% = 100 |
| Decrease Y by P% | Y x (1 - P / 100) | 100 - 20% = 80 |
| Original before a P% change | new / (1 ± P / 100) | 72 after -20% was 90 |
| Percentage difference | |A - B| / ((A + B) / 2) x 100 | 80 and 100 = 22.2222% |
Percent change versus percentage difference
Percent change has a direction: it measures from an old value to a new one, so 80 to 100 is +25% while 100 to 80 is -20%. Percentage difference has no direction: it compares two values against their average, so 80 and 100 differ by 22.2222% either way. Use percent change for growth, price changes and before and after. Use percentage difference to compare two quotes or two stores.
Percentage points versus percent
When a rate itself changes, say a conversion rate going from 2% to 3%, it rose by 1 percentage point, which is a 50% increase. Both statements are true, and mixing them up is a common reporting error. The last box shows both.
Percentages for sellers and store owners
Discounts
A 25% discount on a $59.99 product: use Decrease 59.99 by 25% to get 44.9925, which your store shows as $44.99. The customer saves $15.00. To work out what a sale price was before the discount, use Original number before a change: $72 after a 20% decrease was $90.
Stacked discounts do not add up. 20% off, then another 10% off the reduced price, is 0.80 x 0.90 = 0.72 of the original, a 28% total discount, not 30%. For full price, saving and percent-off tables, use the discount calculator.
Margin and markup
Margin and markup are both percentages of the same profit, measured against different bases. A product that costs $12 and sells for $30 makes $18 profit. As a percent of the price (X is what percent of Y: 18 of 30) that is a 60% margin. As a percent of the cost (18 of 12) it is a 150% markup. Our profit margin calculator and markup calculator handle these with fees included.
Price increases
Raising a $24.99 price by 8%: Increase 24.99 by 8% gives 26.9892, so $26.99. To see how much a supplier's price rise was, use Percentage change: from $6.40 to $7.04 is a 10% increase.
A cut and a rise of the same percent do not cancel out. A $100 price cut by 20% becomes $80, and raising $80 by 20% gives only $96. To get back to $100 you need a 25% increase, which the Percentage change box confirms (80 to 100).
Growth and conversion rates
Monthly revenue going from $18,500 to $21,275 is a 15% increase. Orders going from 400 to 340 is a 15% decrease. A store with 12,000 visits and 300 orders converts at 2.5% (X is what percent of Y: 300 of 12,000).
When a percentage change needs to happen across a whole catalog, for example raising every price by 8% or setting a 20% sale on a collection, AM Jarvis Bulk Edit Pro applies it to all products at once on Shopify or WooCommerce, with a preview first and one-click undo.
What a discount does to your margin
A discount comes straight out of your margin, not out of the price you think about. A product priced at $50 that costs $30 has a 40% margin. At 20% off, the price is $40 and profit falls from $20 to $10: the margin is now $10 / $40 = 25%, and you earn half as much per sale. To earn the same total profit, you would need to sell twice as many units. Run this before every sale with Add or subtract a percentage (decrease 50 by 20) and X is what percent of Y (10 of 40).
Buy one, get one 50% off
Two $30 items at full price are $60. With the second at half price, the customer pays $45, which is 25% off the pair (Percentage change from 60 to 45). Saying "25% off two" and "BOGO 50%" describe the same deal; the second often sells more because it sounds bigger.
Percent of total
To see where money goes, divide each part by the total. If a month's costs are $6,000 product, $2,400 ads, $1,200 shipping and $400 software, the total is $10,000, so ads are 24% and shipping 12% (X is what percent of Y for each line). Tracking these shares month to month shows which cost is growing faster than sales.
Worked examples step by step
What is 15% of 240?
240 x 15 / 100 = 36. Shortcut: 10% of 240 is 24, 5% is half of that, 12, and 24 + 12 = 36.
45 is what percent of 60?
45 / 60 = 0.75, and 0.75 x 100 = 75%.
18 is 30% of what?
18 / 0.30 = 60. Check: 30% of 60 is 18.
Percent decrease from 250 to 210
(210 - 250) / 250 x 100 = -40 / 250 x 100 = -16%, a 16% decrease.
Sales tax as a percentage
The same boxes work for tax: What is 8.25% of 80 gives $6.60 of tax. For tax by state, including removing tax from a total, use the sales tax calculator.
Handy reference tables
Common discounts on a $79.99 price
| Discount | Sale price | Customer saves |
|---|---|---|
| 10% | $71.99 | $8.00 |
| 15% | $67.99 | $12.00 |
| 20% | $63.99 | $16.00 |
| 25% | $59.99 | $20.00 |
| 30% | $55.99 | $24.00 |
| 50% | $40.00 | $39.99 |
Increase needed to recover from a decrease
| After a drop of | You need a rise of |
|---|---|
| 10% | 11.11% |
| 20% | 25% |
| 25% | 33.33% |
| 50% | 100% |
The second table is why a sale that lowers prices is easy to start and harder to undo: putting a price back after 25% off is a 33% increase in the customer's eyes. Each row is the Percentage change box run from the lower value back to 100.
Percentages in Excel and Google Sheets
Each box has a one-line spreadsheet version. With the first number in A2 and the second in B2:
- X% of Y:
=A2/100*B2(or=A2*B2if A2 is formatted as a percentage) - X is what percent of Y:
=A2/B2, formatted as a percentage - Percent change from A2 to B2:
=(B2-A2)/ABS(A2), formatted as a percentage - Increase A2 by B2%:
=A2*(1+B2/100) - Original before a B2% decrease:
=A2/(1-B2/100)
The most common spreadsheet slip is mixing a cell that holds 20 with one that holds 20%: Sheets and Excel store 20% as 0.2, so =A2*B2 gives very different answers depending on how B2 was typed.
Quick mental math
- 10%: move the decimal point one place left. 10% of 86 is 8.6.
- 5%: half of 10%. 5% of 86 is 4.3.
- 1%: move the decimal two places. 1% of 86 is 0.86, so 3% is 2.58.
- Swap the numbers: X% of Y equals Y% of X. 8% of 25 is the same as 25% of 8, which is 2.
- 25%, 50%, 75%: a quarter, a half and three quarters.
Growth over several periods
Percentage changes compound. Revenue growing 5% a month for 12 months does not grow 60%; it grows by a factor of 1.05 to the power of 12, which is 1.7959, so 79.59%. In the other direction, losing 10% and then gaining 10% leaves you at 99% of where you started. To find the monthly rate behind a yearly change, take the 12th root: doubling in a year is about 5.95% a month. Use the Percentage change box on the start and end values to check any period.
Common mistakes
- Dividing by the wrong number in percent change. Always divide by the starting value. 80 to 100 is 20 / 80 = 25%, not 20 / 100 = 20%.
- Removing a percentage by subtracting it. A price that includes 20% VAT is not reduced by 20% to find the net price. Divide by 1.20 instead (the Original number box does this).
- Adding percentages that apply in sequence. Two 10% increases make 21%, not 20%.
- Calling a points change a percent change. 2% to 3% is +1 point and +50%.
Troubleshooting
Why does percent change from 0 say n/a?
Any increase from zero is infinitely large as a percentage, so there is no meaningful answer. The box tells you the absolute change instead.
The result has many decimals
Results are rounded to 4 decimal places. Round money to cents yourself, or use the copy button and format the cell in your spreadsheet.
Which box do I use for a markup?
Markup is a percent change from cost to price. Put the cost first and the price second in Percentage change: from $12 to $30 is a 150% markup. To go from cost to price at a set markup, use Increase: 12 increased by 150% is 30.
Why do 20% off and 20% on not cancel out?
Each percentage applies to a different base. 20% off $100 is $20, but 20% on $80 is only $16, so you end at $96. The Original number before a change box gives the right way back.
Can I use negative numbers?
Yes. Percent change uses the absolute value of the starting number, so a loss shrinking from -200 to -150 shows as a 25% increase.