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Percent Change

Increase or decrease between two values.

Math & NumbersUpdated 2026-04-05• Author: CalcDock Team, Math reference editor• Reviewed by: CalcDock Team, Editorial review: directional % change vs zero baseline (Apr 2026)

The Percentage Change Calculator finds the exact percentage increase or decrease between two values. Whether you're analyzing a price change, comparing this year's revenue to last year, tracking weight loss progress, or calculating a salary raise percentage, the formula is the same: divide the change by the original value and multiply by 100. This calculator also handles the reverse — enter a starting value and a desired percentage change to find the new value. Understanding percentage change is one of the most practical math skills for finance, business, and daily life.

When this calculator helps most

Use when you have an old and new value and need relative change, or forward from old + percent to new.

What each input means

Old value — Baseline “before” amount — usually the denominator of the change. (number)
New value — “After” amount — the comparison endpoint. (number)

Input mistakes to avoid

•Old value must be non-zero for percent change.
•Keep units consistent (both in dollars, both in kg, etc.).

Percent Change

Original Value

New Value

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Formula

Percentage Change = ((New − Old) / |Old|) × 100

Examples

Price Increase: $80 to $100

A product's price increased from $80 to $100. What is the percentage increase?

→ 25% increase

Revenue Growth: $1.2M to $1.8M

Annual revenue grew from $1.2M to $1.8M. What is the year-over-year growth rate?

→ 50% increase

Salary Negotiation: $65,000 to $74,750

A salary increase from $65,000 to $74,750. What percentage raise is this?

→ 15% increase

Price Drop in Market Downturn

Asset value dropped from $250,000 to $187,500. What is the percentage decrease?

→ 25% decrease

How to read your results

→Percent change = (new − old) ÷ |old| × 100; sign shows direction.
→Old = 0 is undefined for relative change — use absolute difference or another baseline.
→Reversing a % increase uses division by (1+r), not subtracting r% from the new value.

What this result means

The percent tells you relative movement from the baseline — not absolute dollars unless you multiply back.

Common Pitfalls

⚠️Chaining % up then % down and expecting to return to the start — multiplicative effects.
⚠️Using symmetric “% difference” when reporting directional growth — definitions differ.
⚠️Tiny old values that explode the percentage — report absolute change too.

Tips

✓A 50% increase followed by a 50% decrease does NOT return to the original value — it ends 25% lower.
✓To reverse a percentage change, divide by the factor (e.g., divide by 1.20 to reverse a 20% increase).
✓For multi-year growth, use CAGR rather than simple percentage change to account for compounding.
✓When reporting changes, always specify the reference period — "25% increase vs last quarter" vs "vs last year" can look very different.

How to check your results

✓Change = new − old; % = change/old × 100.

Warnings & Limitations

⚠️Financial and medical metrics may need seasonally adjusted or population-adjusted baselines.

What this calculator does not tell you

–Annualized CAGR over multiple years — that needs geometric mean / compound formulas.
–Percentage point moves between two rates — that is absolute, not this relative change.

Frequently Asked Questions

What is the formula for percentage change?

Percentage Change = ((New Value − Old Value) / |Old Value|) × 100. A positive result means an increase; negative means a decrease.

What is the difference between percentage change and percentage difference?

Percentage change measures change from an original value (directional — has a "before" and "after"). Percentage difference is symmetric and measures difference relative to the average of two values, used when neither value is a reference point.

Does a 50% decrease followed by a 50% increase return to the original value?

No. Starting at 100: after 50% decrease = 50. Then 50% increase of 50 = 75. You end up at 75, not 100. Percentage changes are multiplicative, not additive.

How do I reverse a percentage increase?

To find the original value before a percentage increase, divide by (1 + rate). Example: After a 25% increase, the value is $125. Original = $125 / 1.25 = $100. Do NOT subtract 25% from $125 — that gives $93.75 (wrong).

What is a year-over-year (YoY) percentage change?

Year-over-year change compares a metric (revenue, sales, traffic) to the same metric 12 months prior. Formula: (Current Year − Prior Year) / Prior Year × 100. It removes seasonal fluctuations by comparing equivalent periods.

What is CAGR (Compound Annual Growth Rate)?

CAGR measures the steady annual growth rate over multiple years: CAGR = (End Value / Start Value)^(1/Years) − 1. Unlike simple percentage change, CAGR accounts for compounding and is a more meaningful measure of long-term growth.