Toolphy

Percentage Increase Calculator

Measure a percentage increase or decrease between two values, or work out the new value after a percentage change. Three modes, with the formula and absolute delta shown.

How to Use the Percentage Increase Calculator

The Percentage Increase Calculator handles three related questions in one place: how much a value grew, how much it shrank, and what a value becomes after a known percentage change. Each mode displays the exact formula with your numbers substituted, plus the absolute difference, so you always see how the answer was produced. All calculations run instantly in your browser and nothing is uploaded.

  1. Pick a mode. Use the tabs at the top to switch between Percentage Increase, Percentage Decrease and New Value After Change. In the first two modes you compare a starting value with a final value; in the third you start from an original value and apply a percentage change.

  2. Enter your numbers. For an increase, type the starting value and the final value — for example 80 and 100. For a decrease, enter the larger value first, such as 100, then the smaller one, such as 80. For the new-value mode, enter the original value and the percentage, then choose whether it is an increase or a decrease.

  3. Read the result. The tool shows the percentage change, the absolute delta (the plain difference between the two values), and the formula with your inputs filled in. Example: going from 80 to 100 is a 25% increase with a delta of 20; going from 100 to 80 is a 20% decrease, also with a delta of 20.

  4. Copy the answer. Press Copy result to send the value and its formula to your clipboard, ready to paste into a report, a spreadsheet or a message.

What Is a Percentage Increase?

A percentage increase expresses how much a value has grown relative to its original size. It is calculated by subtracting the original value from the new value, dividing by the original value, and multiplying by 100: ((new − original) ÷ original) × 100. If a price rises from $80 to $100, the increase is ((100 − 80) ÷ 80) × 100 = 25%. A percentage decrease uses the same structure but measures a drop: ((original − new) ÷ original) × 100, so a fall from 100 to 80 is a 20% decrease. The denominator is always the original starting value, which is why a 20% decrease followed by a 25% increase brings you back to the beginning rather than a 20% increase. Because the base changes each time, percentage changes are not symmetric, and this trips up a lot of people. Knowing which value sits in the denominator is the single most important habit for reading percentage change correctly. You can also run the calculation in reverse. To find a new value after a percentage change, multiply the original by (1 + change ÷ 100) for an increase, or (1 − change ÷ 100) for a decrease. For example, a 15% increase on 200 is 200 × 1.15 = 230, while a 15% decrease on 200 is 200 × 0.85 = 170.

Common Applications

1. Retail and discounts: A jacket drops from $120 to $84. The tool confirms a 30% decrease, matching the advertised saving.

2. Business and SaaS metrics: Monthly signups grow from 500 to 650 — a 30% increase that is easy to report to stakeholders.

3. Finance and investing: A portfolio moves from $10,000 to $12,500, a 25% gain, or the reverse as a loss, helping compare performance across assets.

4. Salary and pricing: A raise from $50,000 to $58,000 is a 16% increase; a 6% price rise on a $40 plan gives a new value of $42.40.

5. Health and fitness: A runner improves a 10 km time from 60 to 51 minutes, a 15% decrease in duration.

Percentage Increase vs Percentage Points

A percentage point is the plain arithmetic difference between two percentages, while a percentage increase is relative. If a rate climbs from 10% to 15%, it rose by 5 percentage points — but the relative increase is ((15 − 10) ÷ 10) × 100 = 50%. This calculator returns the relative percentage change, not the difference in percentage points.

How to Reverse a Percentage Change

To undo a percentage change, do not simply subtract the same percentage. Start from the final value, then divide by (1 + change ÷ 100) for an increase, or by (1 − change ÷ 100) for a decrease. If a price of $120 is the result of a 20% increase, the original was 120 ÷ 1.2 = $100.

Guides

Frequently Asked Questions - FAQ

Is my data safe using this tool?

Yes. Every calculation is performed locally by JavaScript in your browser. No numbers are transmitted and nothing is stored on a server.

How do I calculate a percentage increase?

Subtract the starting value from the final value, divide the result by the starting value, then multiply by 100. For example, 80 to 100 gives ((100 − 80) ÷ 80) × 100 = 25%.

What is the difference between a percentage increase and percentage points?

A percentage point is the arithmetic gap between two percentages (10% to 15% is 5 percentage points). A percentage increase is relative to the base (10% to 15% is a 50% increase). This tool reports the relative increase.

Can I calculate a percentage decrease instead?

Yes. Switch to the Percentage Decrease tab and enter the larger value as the starting value and the smaller one as the final value. The tool will show the percentage drop and the absolute change.

Why is a 20% decrease not undone by a 20% increase?

Because the base value changes. Losing 20% of 100 leaves 80, and a 20% increase on 80 only returns you to 96. You would need a 25% increase on 80 to get back to 100.

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