Percentage Increase Calculator

A percentage increase tells you how much something grew compared to where it started.

The calculator uses one formula:

(new number − old number) ÷ old number × 100

That's it. Three steps, done.

What each part means

Old number — the starting value. The price before a sale. Your weight last month. The score you had before you studied.

New number — the value you ended up with. The price now. Your weight this month. Your score after studying.

Subtract first — take the new number and subtract the old number. This gives you the raw change — how much was actually added.

Divide by the old number — this turns the raw change into a share of where you started. A change of 10 means something different if you started at 20 versus if you started at 200.

Multiply by 100 — this converts it into a percentage, the number you recognize.

A quick example

Say a jacket costs $40, then the price goes up to $50.

• Subtract: $50 − $40 = $10
• Divide by the old price: $10 ÷ $40 = 0.25
• Multiply by 100: 0.25 × 100 = 25%

The price increased by 25%.

When the result is negative

If the new number is smaller than the old number, the subtraction gives a negative result. That means the value went down, not up. The calculator will show a negative percentage, which is a decrease.

These three terms sound similar. They mean different things.

Percentage increase

Use this when a number goes up.

You start with the old number. The new number is bigger. The result is positive.

Your rent went from $800 to $900. That's a 12.5% increase.

Percentage decrease

Use this when a number goes down.

You use the same formula. But the new number is smaller than the old one. So the result comes out negative — or you flip it and call it a decrease.

A jacket was $120. It's now $90. That's a 25% decrease.

Both use the same math: (new − old) ÷ old × 100. The sign tells you the direction.

Percent change

"Percent change" covers both directions. It's the umbrella term.

• Positive result → things went up (an increase)
• Negative result → things went down (a decrease)

This calculator gives you percent change. If your answer is positive, you got a percentage increase. If it's negative, the value fell.

Which one should you use?

When in doubt, run the numbers. The sign does the work for you.

Mixing up old and new

The most common mistake is putting the numbers in the wrong spots.

You always divide by the old number — the starting value. If you flip them and divide by the new number instead, you get a different answer. And it will be wrong.

Example: Price went from $40 to $52.

• Right way: ($52 − $40) ÷ $40 × 100 = 30%
• Wrong way: ($52 − $40) ÷ $52 × 100 = 23%

When in doubt, ask yourself: "What did it start at?" That number goes on the bottom.

Starting with zero

If your old number is 0, the formula breaks.

You can't divide by zero. It's not a calculator bug. It's just not possible. A percentage increase only makes sense when there's a starting value to compare against.

If something goes from 0 to anything, the percentage increase is undefined. You can say it grew by a certain amount, but you can't express that growth as a percentage increase.

Starting with a negative number

This one trips people up.

Say a company lost $50 last year (−$50) and made $100 this year. Plug it in:

($100 − (−$50)) ÷ (−$50) × 100 = $150 ÷ (−$50) × 100 = −300%

A negative result here doesn't mean the number went down. It means your starting number was negative, which flips the sign. The math is correct, but it's hard to read as a meaningful "increase."

For negative starting values, it's usually clearer to describe the change in plain numbers rather than as a percentage.

Getting a negative result when you expected positive

If your answer comes out negative, check two things:

1. Did you subtract in the right order? It should be new minus old, not old minus new.
2. Is your new number actually smaller than the old one? If yes, the value went down — that's a percentage decrease, not an increase.

Confusing percentage increase with percentage points

If an interest rate goes from 2% to 5%, most people say it went up by 3%. That's true in percentage points.

But the percentage increase is: (5 − 2) ÷ 2 × 100 = 150%

These two things measure different things. Percentage points count the raw gap. Percentage increase measures how big that gap is compared to where you started. This calculator gives you the percentage increase.

You need this calculator any time a number goes up and you want to know how much it went up — as a percentage.

Here are the situations where it comes up most.

Prices and bills

Prices change all the time. Groceries, rent, utilities, subscriptions. When something costs more than it used to, a percentage tells you whether the increase is small or significant.

• Your electric bill went from $95 to $114. How bad is that?
• A streaming service raised its price from $12 to $17. Worth keeping?
• Gas was $3.20 last month and is $3.75 today. How much did it jump?

Plug in the old price and the new price. You get your answer in seconds. If a price is going down instead of up, the Discount Calculator is the faster tool for that.

Salary and income

When you get a raise, your employer might tell you the dollar amount. But the percentage is what matters for comparing offers or tracking progress over time.

• You made $48,000 last year. You now make $51,500. What percent raise did you get?
• A job offer promises a $4,000 increase. Is that a lot compared to your current pay?

School and test scores

Students and parents use this to track improvement between tests or semesters.

• You scored 68 on the first test and 79 on the second. How much did you improve?
• Your GPA went from 2.8 to 3.3. What's the percentage increase?

Business and sales numbers

If you run a business or track performance at work, percentage increases show up constantly.

• Sales were $22,000 last month and $27,500 this month. How much did revenue grow?
• Website visits went from 1,200 to 1,850. What's the growth rate?

Health and fitness

Tracking physical progress often means comparing numbers over time.

• You could do 12 push-ups three months ago. Now you can do 19. How much stronger are you?
• Your weekly step count went from 28,000 to 35,000. What's the improvement?

If you have an old number, a new bigger number, and you want to know how much it grew — this calculator is the right tool. For restaurant bills where you need to figure out a tip, the Tip Calculator handles that math instead.

This calculator is for informational use only; double-check any value that affects a real decision.