Growth and return
CAGR calculator
Compound annual growth rate is the steady yearly rate that would have taken a starting value to an ending value over a given number of years. It deliberately smooths the path, which is what makes it comparable and what makes it misleading.
Value at the beginning of the period
Measured the same way as the start
Years between the two, one fewer than data points
The formula
- Starting value
- The value at the beginning of the period. This input carries more weight than it appears to, because the rate is highly sensitive to where you start. A weak first year produces a flattering rate, and choosing the base year is frequently how a growth claim gets manufactured rather than measured.
- Ending value
- The value at the end of the period. Both figures need to be measured the same way. Revenue against revenue, contribution against contribution. A period where the definition changed partway through, or where an acquisition arrived, produces a rate describing two different businesses.
- Years
- The number of years between the two figures, which is one fewer than the number of annual data points. From the end of 2020 to the end of 2023 is three years, not four. Getting this wrong is the most common mechanical error on this calculation and it always understates the rate.
A worked example
The outdoor gear brand grew from 1,000,000 to 1,600,000 over three years. That is a compound annual growth rate of about 17 percent, which is the figure that goes in the deck and the bank conversation.
The path was not steady. Year one went to 1,400,000, a forty percent jump. Year two fell to 1,100,000, a twenty-one percent decline that very nearly ended the business. Year three recovered to 1,600,000. The CAGR is still 17 percent, because CAGR only looks at the two ends and ignores everything between them. It describes a smooth climb that did not happen and cannot see the year that almost broke the company.
Now move the starting line. Measured from the 1,400,000 peak in year one to the same 1,600,000 ending value, the rate over two years is 6.9 percent. Same business, same final figure, and the growth rate is either 17 percent or 7 percent depending entirely on which year someone chose to start from. When a growth rate appears in a pitch without the period stated plainly, that is the first thing worth asking about.
One more trap in the same numbers. Averaging the three annual rates of plus forty, minus twenty-one, and plus forty-five gives 21 percent, which is four points above the real answer. Growth rates compound rather than add, so the ordinary average always overstates them whenever the path was volatile. CAGR is the correct calculation and the mental shortcut is not.
When to use it
CAGR earns its place whenever periods of different lengths have to be compared on one axis. A five year investment and an eighteen month one cannot be judged against each other on total return, but they can on an annualised rate. This is exactly the gap in ROI, which reports the same fifty percent whether it took a month or a decade.
It is the right way to state a growth target as well as to report one. A target expressed as a compound rate builds in the fact that each year starts from a larger base, which is why a business doubling in five years needs about fifteen percent a year rather than the twenty a straight division suggests.
Use it alongside the annual figures rather than instead of them. The rate is the summary and the year-by-year numbers are the evidence. Anyone presenting the first without being willing to show the second is asking to be trusted rather than read.
Where it misleads
The smoothing is the entire point and the entire problem. Two businesses with identical CAGR can carry completely different risk, one growing steadily and one that collapsed and recovered. Nothing in the rate distinguishes them, and the volatile one is considerably more likely to have a bad year again.
Endpoint selection determines the answer. Whoever picks the two dates picks the rate, and because the calculation looks rigorous the choice tends to escape scrutiny. A base year that happened to be poor will produce an impressive figure indefinitely. Compare periods of equal length, and be suspicious of any period whose boundaries look chosen rather than natural.
It is not the average of the annual growth rates, and the difference is not small. Compounding means the ordinary average overstates growth whenever the path was uneven, and the more volatile the period the wider the gap. Anyone reconciling two figures that will not agree is usually comparing a geometric rate against an arithmetic one.
A rate says nothing about size. Growing from 10,000 to 20,000 and from 10,000,000 to 20,000,000 both report the same rate, and small bases produce spectacular percentages that mean very little. Read the rate next to the absolute figures, particularly on anything early stage.
It is a description of the past being routinely used as a forecast. Extending a historical CAGR forward assumes the conditions that produced it continue, which is a claim about the future rather than a measurement, and it deserves to be argued rather than assumed. For the brand above, the 17 percent was funded by an acquisition programme the LTV to CAC ratio shows is running at half the level it needs, which makes projecting it forward a very different proposition.
Frequently asked
What is a good CAGR?
It depends entirely on the asset and the period. Broad equity markets have historically returned roughly seven to ten percent a year over long horizons, while a young business growing at fifteen percent may be underperforming its sector. The rate only means something against a relevant comparison over the same length of time.
What is the difference between CAGR and average annual growth rate?
Average annual growth adds the yearly rates and divides by the number of years. CAGR compounds them, so it reflects the fact that each year builds on the last. The simple average is always the higher of the two when growth was uneven, and CAGR is the figure that actually connects the starting and ending values.
Can CAGR be negative?
Yes. A negative rate means the ending value is below the starting value, and it expresses the steady annual decline that would have produced that result. The calculation breaks down entirely if either value is zero or negative, since there is no rate that grows from nothing.
Why does my CAGR differ from averaging the yearly percentages?
Because growth compounds rather than adds. A year of plus fifty followed by a year of minus fifty leaves you at seventy-five percent of where you started, not back at even. The ordinary average reports zero, and only the compound rate reflects what actually happened.
How many years should the calculation cover?
Long enough to cover a full cycle rather than a favourable stretch, which for most businesses means three to five years. Shorter periods are dominated by whatever happened to be unusual about the endpoints. Whatever period is used, state it alongside the rate, because the two are meaningless apart.
Numbers are the easy part
Getting the calculation right takes two inputs. Getting an organization to agree on what counts as gain, what counts as cost, and what the number should change takes considerably longer.
That translation work is most of what I do. Westphal Solutions builds websites, tools, and reporting for nonprofits and growing teams, including the kind of measurement setup that makes a number like this one worth trusting in the first place.
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