Find percent increase or decrease between two numbers — instantly, as you type. Plus three more percentage modes.
A percentage change tells you how much a number has grown or shrunk relative to where it started, expressed as a percentage. It is the single most useful way to compare two figures — a price last month versus this month, your weight in January versus June, last year's revenue versus this year's, or a test score before and after studying. Raw differences can mislead (a €10 rise on a €20 item is huge; the same €10 on a €2,000 laptop is trivial), so percentage change puts every comparison on the same scale.
This tool covers the four percentage questions people actually search for, all in one place and all updating the instant you type:
Unlike the big generalist calculator sites that hide the answer behind a "Calculate" button and a wall of ads, BreezeCalc shows the number above the fold and recalculates live on every keystroke — no sign-up, no waiting, fast on mobile. That speed is the whole point: get the answer, see how it was worked out, and move on.
The formula for percent change between an old (starting) value and a new (ending) value is:
Percentage change = (New − Old) ÷ |Old| × 100
The result is positive for an increase and negative for a decrease. We divide by the old value because that is the baseline you are comparing against — this is the part people get wrong most often. We use the absolute value of the old number so the sign of the change is driven by the direction of movement, not by a negative starting point.
The related formulas the other modes use:
| Question | Formula |
|---|---|
| What is P% of N? | N × P ÷ 100 |
| X is what % of Y? | X ÷ Y × 100 |
| Increase N by P% | N × (1 + P ÷ 100) |
| Decrease N by P% | N × (1 − P ÷ 100) |
A coffee subscription rises from $12 to $15 a month. Change = (15 − 12) ÷ 12 × 100 = 3 ÷ 12 × 100 = +25%. The price went up by a quarter.
A jacket is cut from £80 to £60. Change = (60 − 80) ÷ 80 × 100 = −20 ÷ 80 × 100 = −25%. It is 25% cheaper. Note that a 25% drop does not undo a 25% rise — percentages are not symmetric, which trips up a lot of people.
Website visitors go from 4,000 to 10,000. Change = (10,000 − 4,000) ÷ 4,000 × 100 = 6,000 ÷ 4,000 × 100 = +150%. A change above 100% simply means the new value is more than double the old one.
| From → To | Difference | % change |
|---|---|---|
| $12 → $15 | +$3 | +25% |
| £80 → £60 | −£20 | −25% |
| 4,000 → 10,000 | +6,000 | +150% |
| 50 → 50 | 0 | 0% |
| 200 → 100 | −100 | −50% |
Money and budgeting. Track how much a bill, rent or grocery total has gone up year on year, or work out the real size of a pay rise. A jump from $52,000 to $55,000 is a +5.8% raise — worth knowing before you celebrate or negotiate.
Sales and discounts. The "Increase / decrease by %" mode does the maths shop tags expect: a 30%-off £45 item costs £31.50. The "X is what % of Y" mode lets you reverse-engineer a discount you have already been quoted.
Business and analytics. Revenue growth, conversion-rate lift, churn, headcount change — almost every business metric is reported as a percentage change month over month or year over year, because it makes performance comparable across different sizes.
Health and fitness. Bodyweight, lift numbers and running times are easier to judge as percentages: losing 4 kg means more to someone who weighed 65 kg (−6.2%) than to someone who weighed 110 kg (−3.6%).
School and exams. Improving from 58 to 72 marks is a +24% improvement in your score — useful for tracking progress between mock and final.
Always divide by the starting value, not the ending one. Dividing by the new number gives a different (smaller) figure and is the number-one error in percentage change.
A rise and the matching fall are not equal. Going up 50% then down 50% does not return you to the start: 100 → 150 → 75. To fully reverse a 50% increase you need a 33.3% decrease.
Mind "percent" versus "percentage points". If an interest rate goes from 4% to 5%, that is +1 percentage point but a +25% percentage change. News headlines mix these up constantly.
Watch a starting value of zero. Percentage change from 0 is mathematically undefined (you cannot divide by zero), so going from 0 to any number has no finite percentage — report it as "new" instead.
Subtract the old value from the new value, divide by the absolute value of the old value, then multiply by 100. The formula is (New − Old) ÷ |Old| × 100. A positive answer is an increase; a negative answer is a decrease.
They use the same formula. If the new value is bigger than the old value the result is positive and we call it a percentage increase; if the new value is smaller the result is negative and we call it a percentage decrease.
Percentage change measures movement relative to your starting point, which is the old value. That baseline is what makes two changes of different sizes comparable. Dividing by the new value answers a different question and gives the wrong percentage change.
No. Percentages compound on different bases. 100 increased by 50% is 150; 150 decreased by 50% is 75, not 100. To reverse a 50% increase you need a 33.3% decrease.
A percentage point is the simple arithmetic gap between two percentages (4% to 5% is +1 point). A percent change measures that gap relative to the start (4% to 5% is a +25% change). Always check which one a figure refers to.
You cannot — dividing by zero is undefined, so there is no finite percentage change from a starting value of 0. Report the move as "from 0 to N (new)" rather than as a percentage.
Yes, it is completely free with no sign-up. All calculations run in your browser as you type; nothing you enter is sent to or stored on a server.