Percentage Increase Calculator

What this calculator does

This calculator works out the percentage increase between two values — how much one number has grown compared to another, expressed as a percentage of the original. It also runs the reverse workflow: given a starting value and a percentage to apply, it tells you the resulting new value. Both modes show the calculation step by step so you can copy the result, or copy the reasoning into a report or spreadsheet.

How to calculate percentage increase

The formula is:

percentage increase = ((new value − old value) ÷ old value) × 100

Three steps in plain language: subtract the old from the new to get the absolute change, divide by the old (the base against which the growth is measured), then multiply by 100 to express the result as a percentage rather than a decimal. The base is always the original value — that’s the part people get wrong most often, and it’s why swapping the two numbers gives a different answer.

Worked example

A piece of software cost $50 last year and costs $60 this year. The percentage increase is:

Three more for reference:

• Followers go from 1 200 to 1 500 → (300 ÷ 1 200) × 100 = 25 %.
• Revenue goes from $80 000 to $94 000 → (14 000 ÷ 80 000) × 100 = 17.5 %.
• A rent of $1 800 rises to $1 935 → (135 ÷ 1 800) × 100 = 7.5 %.

The calculator above shows the same three-step breakdown live as you type so you can copy it into an email, a slide, or a Sheets cell.

Percentage increase vs percentage difference vs percent change

These three terms sound similar and are routinely confused, but they solve different problems and use different formulas.

• Percentage increase is the positive case: a value has gone up from a known starting point. Denominator is the starting value.
• Percentage decrease is the same idea for the negative case.
• Percentage change is the signed version — positive when the value goes up, negative when it goes down. Same denominator as increase/decrease (the starting value). Use this when the direction isn’t fixed in advance, e.g. tracking a metric that fluctuates.
• Percentage difference is symmetric — it doesn’t matter which value is “first”. The denominator is the average of the two values. Use this when neither value is “the original” — comparing two measurements, two store prices, two model predictions.

A concrete example: comparing 40 and 60.

The same two numbers produce three different percentages. Each is correct for its specific question. Picking the right formula is the work; the arithmetic is easy.

Common mistakes to avoid

Dividing by the new value instead of the old. The denominator is always the original value. Dividing by the new value silently underestimates the growth. If the old value was 50 and the new is 60, correct answer is 20 % — using 60 as the denominator gives 16.7 %.

Confusing “increase to X %” with “increase by X %”. “Sales increased to 120 %” of last year means new = old × 1.20. “Sales increased by 120 %” means new = old × 2.20. The little preposition swings the answer by a factor of two.

Compounding percentages incorrectly. A 10 % increase followed by another 10 % increase is not a 20 % increase — it’s a 21 % increase. 1.10 × 1.10 = 1.21. The same goes in reverse: a 10 % drop followed by a 10 % gain is a net 1 % loss, not a wash. The Compound Interest Calculator in our suite walks through the multi-period case.

Reporting a negative increase. If the formula spits out a negative number, you have a decrease. Reframe before sending the email. The calculator above does this automatically.

Privacy

This calculator runs as a few arithmetic operations in JavaScript on your device. There are no fetch calls, no analytics on the values you enter, no server-side logging.