Percent Change Calculator

What This Calculator Does

The Percent Change Calculator measures how much a value has increased or decreased relative to its starting point. Enter an original value and a new value, and the tool returns the percentage change between them. A positive result means growth. A negative result means decline.

This is one of the most widely used calculations in finance, economics, and science. The Bureau of Labor Statistics publishes the Consumer Price Index as a percent change. The Bureau of Economic Analysis reports GDP growth as a percent change. Stock analysts, retail managers, and scientists all rely on this formula daily.

The Formula

The percent change formula is:

Percent Change = ((New Value - Original Value) / |Original Value|) × 100

The numerator (New - Old) gives you the absolute change. Dividing by the absolute value of the original gives you the relative change as a decimal. Multiplying by 100 converts it to a percentage.

The absolute value in the denominator matters when dealing with negative numbers. If a temperature rises from -10°C to +10°C, the formula uses |-10| = 10 in the denominator, giving ((10 - (-10)) / 10) × 100 = 200%. Without the absolute value, the result would be -200%, which incorrectly suggests a decrease.

How to Use This Calculator

1. Enter your original value in the "From Value" field.
2. Enter your new value in the "To Value" field.
3. Read the result. Green indicates an increase. Red indicates a decrease.

The calculator updates instantly as you type. You can use decimals, negative numbers, and large values.

Example Calculations

Example 1: Stock Price Increase

Maria bought shares of a tech company at $142.50. Six months later, the stock trades at $178.75. She enters 142.50 as the original value and 178.75 as the new value. The calculator shows a 25.44% increase. Her $5,000 investment grew to $6,272, gaining $1,272.

Example 2: Retail Price Drop

A department store in Chicago marks down a winter coat from $240 to $168 for an end-of-season sale. The percent change is ((168 - 240) / 240) × 100 = -30%. The negative sign tells us the price dropped by 30%. Shoppers can verify this against the store's advertised "30% off" sign.

Example 3: Revenue Growth Between Quarters

A small bakery in Austin reported $48,000 in Q1 revenue and $61,000 in Q2. The percent change is ((61,000 - 48,000) / 48,000) × 100 = 27.08%. The owner can compare this to industry benchmarks. According to the National Restaurant Association's 2026 Industry Outlook, independent bakeries averaged 6.2% year-over-year revenue growth, so this bakery is outperforming its peers significantly.

Real-World Scenarios

Tracking Inflation with CPI

The Consumer Price Index measures inflation as a percent change. In June 2026, the BLS reported a 3.0% year-over-year CPI increase, down from 3.2% in May. You can use this calculator to verify those numbers. If the CPI was 314.2 in June 2025 and 323.6 in June 2026, the percent change is ((323.6 - 314.2) / 314.2) × 100 = 2.99%, which rounds to the reported 3.0%.

Analyzing Website Traffic Drops

A marketing manager notices her company's website traffic fell from 45,000 monthly visitors to 31,500 after a Google algorithm update. The percent change is ((31,500 - 45,000) / 45,000) × 100 = -30%. She needs a 42.86% increase to recover to the original level, not 30%. This asymmetry is a common source of confusion. A 30% drop requires more than a 30% gain to undo.

Comparing Salary Offers

Jordan, a software engineer in Denver, earns $95,000. He receives a job offer for $118,000. The percent change is ((118,000 - 95,000) / 95,000) × 100 = 24.21%. He can use this to negotiate. If his current employer counters with a 15% raise to $109,250, he can compare the two offers directly: 24.21% versus 15%. For a more complete picture of his purchasing power, he might also use our Salary Calculator to account for tax implications.

Common Mistakes to Avoid

• Confusing percent change with percentage points. If mortgage rates rise from 6.5% to 7.0%, that is a 0.5 percentage point increase. But the percent change is ((7.0 - 6.5) / 6.5) × 100 = 7.69%. These are very different numbers, and mixing them up leads to incorrect conclusions.
• Dividing by the new value instead of the original. The denominator must always be the starting value. If a price drops from $100 to $80, the change is -20% (divide by 100, not 80). Dividing by 80 would give -25%, which is wrong.
• Assuming percentage changes are symmetric. A 50% increase followed by a 50% decrease leaves you at 75% of the original, not 100%. This is because the second percentage is calculated from a larger base. Our Percentage Calculator can help you work through these scenarios step by step.
• Forgetting the absolute value with negative numbers. If a value changes from -40 to -20, the percent change is ((-20 - (-40)) / |-40|) × 100 = +50%. This is an increase, even though both values are negative. Using -40 without the absolute value would give -50%, which incorrectly suggests a decrease.

Limitations

Percent change is undefined when the original value is zero. The calculator will display a message in that case. If you are tracking growth from a zero baseline, use absolute change instead.

Percent change can also be misleading when comparing values of very different magnitudes. A 100% increase from 1 to 2 is numerically impressive but practically small. A 5% increase from $1,000,000 to $1,050,000 is numerically modest but practically significant. Always consider the absolute change alongside the percentage.

For scientific applications where you need to compare an experimental result to a theoretical value, our Percent Error Calculator is more appropriate. Percent error uses a different formula that measures deviation from an accepted standard.

Authoritative Research & Resources

• Bureau of Labor Statistics — Consumer Price Index — The BLS publishes monthly CPI data as percent change, which is the primary measure of inflation in the United States. Their methodology page explains how percent change is applied to economic indicators.
• Bureau of Economic Analysis — GDP — The BEA reports real GDP growth as a percent change at an annual rate. This is the headline number cited in economic news and is calculated using the same formula as this calculator.
• National Bureau of Economic Research — Business Cycle Dating — The NBER uses percent change in real GDP among other indicators to determine recessions. Two consecutive quarters of negative percent change in real GDP is a common (though unofficial) recession rule of thumb.