functions

Year-Over-Year Change Calculator | Compute YoY Percent Change

Inside the Year Over Year Change Calculator

Behind the inputs above sits one rule: YoY % = (current − previous) ÷ |previous| × 100. The tool evaluates it instantly with the values you enter.

If you are new to year over year change calculator, start with the worked example in the methodology section below — it walks the formula end-to-end with real numbers — then use the quick-reference table for common scenarios.

Quick reference

Previous	Current	YoY
100	115	+15%
200	180	−10%
50,000	62,500	+25%
1.2M	1.5M	+25%

info Year Over Year Change Calculator

Free math calculator — enter your numbers and get an instant, accurate result.

info Private by design

Everything runs locally in your browser. No uploads, no accounts, no tracking.

info Works everywhere

Fully responsive and mobile-friendly — calculate on any device, any time.

info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

YoY growth	Context (revenue)
0–5%	Mature/inflation-level growth
5–15%	Healthy expansion
15–40%	High growth
> 40%	Hypergrowth — rarely sustainable

lightbulb Worked example

Let's say you are using the Year Over Year Change Calculator. Calculates year over year change using YoY % = (current − previous) ÷ |previous| × 100, in real time in your browser. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula YoY % = (current − previous) ÷ |previous| × 100 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: YoY % = (current − previous) ÷ |previous| × 100

The Year Over Year Change Calculator is built on a well-established calculation method. It uses the formula YoY % = (current − previous) ÷ |previous| × 100 to turn your inputs into a reliable result. Calculates year over year change using YoY % = (current − previous) ÷ |previous| × 100, in real time in your browser. The steps are shown on the page so you can follow the reasoning from input to output.

Enter last year’s value and this year’s value for the same period (full year, same quarter, same month).
The tool subtracts for the absolute change and divides by the previous value for the percentage.
The growth multiple (current ÷ previous) is shown for quick compounding maths.

Example: 100 → 115 is +15 absolute, +15% YoY, a 1.15× multiple.

Authoritative source: Wolfram MathWorld

Frequently asked questions

How do you calculate year-over-year change?

Enter the required values into the input fields and press the calculate button. The tool applies the formula YoY % = (current − previous) ÷ |previous| × 100 and returns the result with a short explanation of each step, so you can check the working yourself.

Why compare year-over-year instead of month-over-month?

The Year Over Year Change Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Calculates year over year change using YoY % = (current − previous) ÷ |previous| × 100, in real time in your browser. There is no limit on usage, and it works on any device.

What if the previous value was negative?

The calculator uses the absolute value of the previous period as the denominator: YoY % = (current − previous) ÷ |previous| × 100. This avoids the misleading result that dividing by a negative number would produce, and it clearly shows both the direction and magnitude of the swing. For example, moving from −50 to −25 is a 50% improvement, not a −50% decline.

How do multiple years compound?

Year-over-year changes compound multiplicatively, not additively: three years of 10%, 20%, and 15% growth produce a total factor of 1.10 × 1.20 × 1.15 = 1.518, or 51.8%, not 45%. To average the growth, use the geometric mean, not the arithmetic mean of the percentages. The calculator handles single-period YoY; for multi-year, compound the factors.

Is YoY the same as CAGR?

No — YoY compares one period to the same period a year earlier, while CAGR (compound annual growth rate) is the constant annual rate that would produce the same total growth over multiple years. CAGR smooths the volatility between the endpoints: CAGR = (ending ÷ beginning)^(1/n) − 1. YoY shows the yearly variation; CAGR shows the average trajectory.

How do I calculate week-over-week change, and when is it better than YoY?

Same formula, shorter window: (this week − last week) ÷ last week × 100. Traffic going 4,800 → 5,280 is +10% WoW. WoW spots fast-moving changes but is noisy and blind to seasonality — a retail site is 'down 30% WoW' every week after Black Friday. Use WoW for launches and incidents, YoY for trend truth.

Why does the formula use the absolute value of the previous figure?

It keeps the sign of the result honest when last year's figure was negative. Moving from −$50k profit to +$50k is genuine growth, and dividing by |−50k| reports +200% instead of the −200% a naive division would produce.

What if last year's value was zero?

It is undefined — you cannot divide by zero. In that case report the absolute change instead ('up $40k from $0') or use a different baseline period. A percent change from nothing is mathematically meaningless.

How is this different from a month-over-month change?

Year-over-year compares a period with the same period one year earlier, which washes out seasonality — December retail vs. December retail. Month-over-month captures recent momentum but bounces with seasonal noise. Healthy reporting uses both.

Can a year-over-year change be more than 100%?

Yes, on the upside: doubling is +100%, tripling is +200%. Declines are bounded differently — falling to zero is −100%, and you cannot fall further unless the base itself was negative, which is why the absolute-value form matters.

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Every CalcaTools percentage calculator — percent-of and percent-off math, stacked discounts, retail markup and margin, error and accuracy checks, plus year-over-year change and ratios — with the working shown on every result.