How to Calculate Percentage Increase and Decrease

Percentage increase and decrease are among the most practical math skills you can master (Khan Academy, 'Percentage Increase and Decrease,' 2024, https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-fractions-decimals/cc-7th-percent-increase-decrease/a/percent-increase-and-decrease-review). Whether you are comparing prices, tracking investment returns, or analyzing data trends, knowing how to calculate these values accurately is essential. Use the PercentEase calculator in percent change mode to follow along with all examples.

The formula for percentage increase is: Percentage Increase = ((New Value - Old Value) / Old Value) x 100. A positive result confirms an increase. For example, if your monthly salary goes from $4,000 to $4,500, the percentage increase is ((4,500 - 4,000) / 4,000) x 100 = 12.5%. According to the U.S. Bureau of Labor Statistics, the average annual wage increase in the United States has hovered between 3% and 5% in recent years (BLS, 'Employment Cost Index,' 2024, https://www.bls.gov/eci/), making a 12.5% jump notably above average.

The formula for percentage decrease works the same way but produces a negative result: Percentage Decrease = ((New Value - Old Value) / Old Value) x 100. If a laptop's price drops from $1,200 to $900, the percentage decrease is ((900 - 1,200) / 1,200) x 100 = -25%. You can express this as a 25% decrease. This is the same percentage change formula explained in our article on percentage change formulas, just applied to a decreasing value.

One of the most common mistakes is using the wrong base value. The denominator in the formula must always be the original (old) value — the value you are measuring the change from. Switching the old and new values in the denominator produces an incorrect result. For instance, if a stock rises from $50 to $75, the correct increase is ((75 - 50) / 50) x 100 = 50%. If you mistakenly divide by the new value 75, you get only 33.3%, which is wrong.

Another frequent error involves confusing percentage points with percentage change. If an interest rate rises from 3% to 5%, that is a 2 percentage point increase. However, in percentage terms, it is a ((5 - 3) / 3) x 100 = 66.7% increase. Khan Academy explains that percentage points describe the absolute difference between two percentages, while percentage change measures the relative shift from the original value (Khan Academy, 'Percentage Increase and Decrease,' 2024, https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-fractions-decimals/cc-7th-percent-increase-decrease).

Successive percentage changes are another area where intuition often fails. If a product's price increases by 20% and then decreases by 20%, many people assume the price returns to its original amount. It does not. Starting at $100, a 20% increase brings the price to $120. A 20% decrease from $120 is $24, making the new price $96 — a net loss of 4%. For more examples of how stacked percentages interact, see our guide to everyday percentage tips.

Percentage increase appears constantly in economic reporting. Inflation, reported monthly by the Bureau of Labor Statistics via the Consumer Price Index (CPI), is expressed as a year-over-year percentage change. If the CPI rises from 296 to 305 over 12 months, the inflation rate is ((305 - 296) / 296) x 100 approximately 3.04% (BLS, 'Consumer Price Index,' 2024, https://www.bls.gov/cpi/).

In retail, percentage decrease drives purchase decisions. A '40% off' sale means the new price is 60% of the original. On a $250 item, you pay $250 x 0.60 = $150, saving $100. Stacked discounts do not add. Twenty percent off plus 10% off: $250 x 0.80 x 0.90 = $180, which is 28% off, not 30%. For more shopping calculation tricks, see our percentage discount calculator guide.

In health and fitness, percentage change tracks progress. If your body weight drops from 200 lbs to 185 lbs, the percentage decrease is ((185 - 200) / 200) x 100 = -7.5%, or a 7.5% loss. Trainers and nutritionists commonly use percentage-based goals because they normalize progress across different body types, according to the American Council on Exercise (ACE, 'Weight Loss Guidelines,' 2024, https://www.acefitness.org).

What is the formula for percentage increase and how do you apply it?

The percentage increase formula is ((New Value - Old Value) / Old Value) x 100, where the denominator is always the original (old) value (Khan Academy, 'Percentage Increase and Decrease,' 2024). To apply it: subtract old from new, divide by old, multiply by 100. Example: revenue grows from $180,000 to $225,000. Increase = ((225,000 - 180,000) / 180,000) x 100 = (45,000 / 180,000) x 100 = 25%. A 25% revenue increase. The PercentEase calculator's percent change mode computes this automatically — enter old value, enter new value, read the result.

Why does a 20% increase followed by a 20% decrease not equal zero net change?

A 20% increase followed by a 20% decrease results in a net -4% change because the second percentage applies to a different base than the first (National Council of Teachers of Mathematics, 'Principles and Standards for School Mathematics,' 2000, https://www.nctm.org/Standards-and-Positions/Principles-and-Standards/). Starting at $100: a 20% increase yields $120 (new base). A 20% decrease from $120 = 20% x $120 = $24, leaving $96 — not $100. Algebraically: $100 x 1.20 x 0.80 = $96. The multipliers multiply to 0.96, not 1.00. This is called the base effect and it is why investment analysts prefer compound annual growth rate (CAGR) over simple percentage averages for multi-period performance.

How do you convert a percentage increase into a multiplier for spreadsheet calculations?

To convert a percentage increase into a multiplier, divide the percentage by 100 and add 1: Multiplier = 1 + (Percentage / 100) (Wolfram MathWorld, 'Percent Change,' 2024). A 15% increase gives a multiplier of 1.15. A 7.5% increase gives 1.075. For decreases, subtract from 1: a 15% decrease is a multiplier of 0.85. Multipliers are preferred in spreadsheets because they chain correctly: two consecutive 10% increases = 1.10 x 1.10 = 1.21, a 21% total increase, not 20%. This multiplicative chaining is the basis of compound growth formulas and is why CalcMyCompound (https://calcmycompound.com) uses this approach for compound interest modeling.

Research Note: How Percentage Literacy Affects Financial Outcomes

A growing body of research in financial literacy demonstrates that consumers who understand percentage increase and decrease formulas make significantly better financial decisions across key life domains.

A landmark study by Annamaria Lusardi and Olivia Mitchell (2014, 'The Economic Importance of Financial Literacy: Theory and Evidence,' Journal of Economic Literature) identified three 'Big Three' financial literacy questions used globally, one of which tests percentage calculation ability. Their analysis of Health and Retirement Study data found that respondents who answered all three correctly accumulated approximately 50% more wealth by retirement age than those who answered fewer than two correctly — even controlling for income and education level.

The same researchers found that financial literacy rates in the U.S. are disturbingly low: only 34% of adults could correctly answer all three Big Three questions as of 2018 (FINRA Investor Education Foundation, 'National Financial Capability Study,' 2018, https://www.finrafoundation.org/studies-reports). One of the core deficits was precisely the ability to calculate percentage change — specifically, understanding that a 50% loss followed by a 50% gain does not return to the original value.

This research motivated educational bodies including the National Council of Teachers of Mathematics (NCTM) and the Consumer Financial Protection Bureau (CFPB) to emphasize percentage reasoning in both K-12 mathematics standards and adult financial education programs. The CFPB now explicitly lists percent-change literacy as a component of its 'Spending Tracker' and 'Budget Worksheet' tools, underscoring its real-world importance (CFPB, 'Making a Budget,' 2024, https://www.consumerfinance.gov/consumer-tools/budget/).

For individual users, the practical implication is straightforward: practicing percentage increase and decrease calculations with real-world scenarios — salary negotiations, investment returns, sale prices, and tax estimates — builds the mental schema that protects against common financial errors. The PercentEase percentage calculator provides instant feedback on any percentage calculation, making it a practical tool for both learning and verification.