What it means
Growth is easy to buy and hard to buy cheaply. The growth efficiency index puts a price tag on it, converting a sprawling sales and marketing budget into a single number that answers whether the money spent is producing revenue at a sensible rate.
It is usually calculated quarterly or annually, dividing the period's sales and marketing spend by the increase in annual recurring revenue over the same period. Some businesses use gross new revenue and others use net new revenue after churn, and the net version is the more demanding and more honest of the two.
Lower is better, and the rough convention in subscription software is that below 1.0 is strong, between 1.0 and 1.5 is acceptable, and much above 2.0 suggests the growth engine is consuming more cash than the revenue justifies. The measure is closely related to the CAC ratio and is sometimes used as another name for it.
The number sits alongside payback period rather than replacing it. An index of 1.5 tells you the cost of a dollar of revenue, while payback tells you how many months of gross profit it takes to earn that cost back, and a board wants both.
Timing distortions are the main thing to watch. Marketing spent in one quarter often produces revenue two or three quarters later, so the index is far more meaningful over a rolling twelve months than over any single quarter.
In practice
Real-world examples.
Example
A board reviewing two years of results sees the growth efficiency index move from 1.1 to 1.9 while revenue growth stays flat at 30%. The conclusion is that growth is being sustained by spending more rather than by selling better, and the next budget links marketing increases to efficiency targets.
Example
A vertical software company compares its index across three sales channels and finds self-serve sign-ups at 0.4, inside sales at 1.3 and field sales at 2.6. Rather than shutting down field sales, which lands the largest contracts, it shifts smaller deals down to the cheaper channels.
Example
A private equity investor screening subscription businesses uses the index as a first filter, discarding companies above 2.5 unless there is a clear explanation such as a deliberate land-grab in a new market. The filter cuts a list of forty targets to eleven before any management meetings are booked.
Think of it
“Growth efficiency shows how much growth you get per dollar of sales and marketing spend.
Formula
Calculation
Growth Efficiency Index = Sales and Marketing Spend / Net New Annual Recurring Revenue
A software business spends $4,500,000 on sales and marketing during a financial year. Annual recurring revenue starts the year at $18,000,000 and ends at $21,000,000.
Net New ARR = $21,000,000 - $18,000,000 = $3,000,000
Growth Efficiency Index = $4,500,000 / $3,000,000 = 1.5
The company spent $1.50 for every $1 of new annual recurring revenue. If its gross margin is 80%, each new revenue dollar contributes $0.80 of gross profit a year, so the $1.50 of acquisition cost takes $1.50 / $0.80 = 1.875 years, or roughly 22 months, to repay. Cutting the index to 1.0 by improving conversion rates would shorten that payback to about 15 months without adding a single extra customer.Case study
Seen in the real world.
Vantry Analytics is a fictional company invented to illustrate this measure. It had grown recurring revenue from $6 million to $14 million in three years, and the founders considered the growth story settled until a prospective lender asked how efficient it was.
The finance team calculated a growth efficiency index of 2.4 for the most recent year: $7.2 million of sales and marketing spend against $3 million of net new annual recurring revenue. Breaking it down by segment revealed the cause. Deals below $20,000 in annual value took almost as much sales effort as deals five times larger, and that segment alone was running at an index of 4.1.
Vantry moved small deals to a self-serve sign-up with no sales involvement, cut two field roles, and redirected the budget to the mid-market segment where the index was 1.2. Revenue growth slowed from 27% to 21% the following year, but the blended index fell to 1.4 and cash burn halved. The illustrative point is that the fastest growth and the most efficient growth are rarely the same thing, and a board has to choose deliberately between them.
Watch out
Common mistakes.
- Using gross new revenue while calling it net. Ignoring churn in the denominator flatters the index, sometimes dramatically, in any business losing a meaningful share of its base each year.
- Reading a single quarter as a trend. Sales and marketing spend leads revenue by several months, so one bad quarter often reflects timing rather than a deteriorating engine.
- Excluding costs that genuinely belong in sales and marketing. Sales commissions, marketing salaries, events and agency fees all count, and leaving any of them out produces a number that cannot be compared with anyone else's.
Questions
People also ask.
What is a good growth efficiency index?
In subscription software, below 1.0 is considered strong, 1.0 to 1.5 is normal, and above 2.0 usually prompts questions about channel mix or pricing.
How does it differ from customer acquisition cost?
Customer acquisition cost is spend per customer won, while the growth efficiency index is spend per dollar of new recurring revenue, which handles businesses with very different deal sizes far better.
Can a very low index be a bad sign?
It can, because an index far below the market norm sometimes means a company is underinvesting in growth and leaving demand unserved rather than being unusually efficient.
From the founder's library
Take it further with the book.
Build your financial confidence beyond this definition. Shihan's full-length guide, Accounting Fundamentals, takes the same plain-English approach and turns it into a complete, practical playbook for non-finance managers, business owners and students - with chapter-end quiz answers and presentation slides included.
25% off with code MMHQ25, applied at checkout. Priced in USD - checkout may show the equivalent in your local currency.
View the book and save 25%