Percentage Increase Calculator

The value you started with. This is the number you divide by.
The value you ended with.

Try it: 50 → 65 is a 30% increase. 1,200 → 900 is a 25% decrease.

How to use this calculator

Enter the value you started with in the “Old value” box and the value you ended with in the “New value” box, then press Calculate. You will get three things: how much the value changed in absolute terms, the change as a percentage, and a plain-English verdict — increase, decrease, or no change. The working is shown underneath, with your own numbers filled in, so you can check every step.

The formula

Percentage change = (new value − old value) ÷ old value × 100

That is the whole method, in three steps:

  1. Subtract: new value − old value. This gives the absolute difference.
  2. Divide that difference by the old value — always the old value, never the new one.
  3. Multiply by 100 to turn the decimal into a percent.

A positive answer means an increase, a negative answer means a decrease, and zero means nothing changed.

Worked example

Say a gym membership cost $50 last year and $65 this year. What is the percentage increase?

  1. Difference: 65 − 50 = 15
  2. Divide by the old value: 15 ÷ 50 = 0.3
  3. Multiply by 100: 0.3 × 100 = 30%

The membership went up by $15, which is a 30% increase. As a cross-check, the new price is 130% of the old price (65 ÷ 50 × 100), and 130% − 100% = 30%. If the numbers do not line up that way, something went wrong in step 2 — check which value you divided by.

A decrease works exactly the same way. If website traffic fell from 1,200 visits to 900 visits: (900 − 1,200) ÷ 1,200 × 100 = −25%, a 25% decrease of 300 visits.

When you would use this

Price changes, salary raises, rent increases, weight change, follower growth, sales month over month, test-score improvement — anywhere you have a “before” and an “after” and want to know how big the move was relative to where it started. The percentage matters because it puts changes on the same scale: a $15 rise on a $50 item (30%) is a much bigger deal than a $15 rise on a $1,500 item (1%).

Common mistakes box

  1. Percentage points are not the same as percent. If support for a policy rises from 10% to 12%, that is a rise of 2 percentage points — but a 20% increase relative to where it started ((12 − 10) ÷ 10 × 100 = 20%). Saying “it rose by 2%” understates the move tenfold. Use “percentage points” when both numbers are already percents.
  2. Divide by the old value, not the new one. For 50 → 65, dividing 15 by the new value (65) gives 23%, which is wrong. The question is “how much did it grow compared with where it started,” so the old value is always the denominator.
  3. A 100% increase means doubling. 100% of the old value added on top gives twice the old value. A 200% increase means tripling, not doubling.
  4. You cannot calculate a percentage change from zero. If the old value is 0, the formula asks you to divide by 0, which has no answer. This calculator says so plainly and still gives you the absolute difference. Likewise, treat a negative starting value with care: the sign of the result can look backwards, so read the absolute difference alongside the percent.
  5. Do not add percentages from different bases. A 10% rise followed by a 10% fall does not bring you back to the start — the fall applies to the new, larger value, so you end up 1% below where you began.

Frequently asked questions

  1. What is the percentage increase formula? Percentage increase = (new value − old value) ÷ old value × 100. Subtract first, divide by the starting value, then multiply by 100.
  2. How do I calculate percentage increase between two numbers? Find the difference between the two numbers, divide that difference by the original (old) number, and multiply by 100. Example: 50 → 65 is (65 − 50) ÷ 50 × 100 = 30%.
  3. What if the new value is smaller — is it still a percentage increase? No. If the new value is smaller, the same formula gives a negative result, which is a percentage decrease. This calculator labels it as a decrease and shows the size of the drop, for example 1,200 → 900 is a 25% decrease.
  4. Can I calculate percentage increase from 0? No — a percentage change from 0 is undefined because the formula divides by the old value and you cannot divide by 0. If you started at 0, report the absolute difference instead (for example, “up by 40 units”).
  5. What is the difference between percent and percentage points? Percent is a relative change; percentage points are the plain arithmetic gap between two percentages. Going from 10% to 12% is +2 percentage points, which is a 20% relative increase.
  6. Why do I get a different answer when I divide by the new value? Because that answers a different question — how big the change is compared with the ending value. The standard percentage-change formula always uses the starting value as the base, so divide by the old value.

Disclaimer

This calculator is for general information and everyday math only. It is not financial, tax, or investment advice. Results are rounded to two decimal places; for contracts, payroll, or tax filings, confirm the figures with the official source or a qualified professional.

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