Growth Efficiency Index: How Much Growth Are You Getting Per Dollar Spent? (2026)

The growth efficiency index divides everything you spent on sales and marketing in a period by the new annualised gross profit that spend produced. A result of 1.0 means a dollar of spend bought a dollar of recurring gross profit. It is a whole-business ratio rather than a per-channel one, which is exactly why it catches problems that channel-level acquisition cost hides.

What It Catches That CAC Does Not

Per-channel acquisition cost is computed on attributed customers, so any spend that produced no attributable customer simply vanishes from the calculation. Brand campaigns, abandoned experiments, sales hires who did not work out, and the management layer above the reps all sit outside channel-level figures. The efficiency index divides by nothing and includes all of it.

It also uses gross profit rather than customer count, so a period where you won many small customers instead of a few large ones shows up honestly. Customer count can rise while the value acquired falls, and only a value-based ratio shows that.

Calculating It Without Flattering Yourself

Include every cost that exists to win revenue: media, all sales and marketing salaries and commissions, the tooling stack, agency fees, events, and the share of leadership time spent on go-to-market. Then measure the new annualised gross profit added in the same period, not revenue, and not bookings you have not delivered.

One timing subtlety matters. Spend in a quarter often produces revenue in the next one, so compare spend in a period against gross profit added in the following period when your sales cycle is long. Aligning them by calendar quarter with a 90-day cycle understates efficiency badly.

1. Total all sales and marketing cost for the period, salaries and tools included.
2. Measure new gross profit added, annualised, from customers won in the matched period.
3. Offset for the sales cycle: lag the gross profit window by roughly one cycle length.
4. Divide spend by gross profit added to get the index.
5. Track it for four consecutive quarters, since one quarter is dominated by timing.

                Q1
  Sales and marketing spend            $340,000
  New customers                              210
  New monthly gross profit added        $22,050
  Annualised  22,050 x 12              $264,600
  Index   340,000 / 264,600                 1.29
Q2 (grew headcount, added brand spend)
  Sales and marketing spend            $520,000
  New customers                              255
  New monthly gross profit added        $24,225
  Annualised  24,225 x 12              $290,700
  Index   520,000 / 290,700                 1.79
Blended CAC barely moved: $1,619 to $2,039.
The index moved 39%, because the extra spend
bought coordination overhead, not customers.
              

The acquisition cost figure made Q2 look like normal channel scaling. The efficiency index showed that $180,000 of additional spend produced $26,100 of additional annual gross profit, which is a return no channel report would have flagged.

Using It as a Spending Control

Set a ceiling and treat it as the condition for increasing budget. If the index stays under your ceiling, spend more; if it crosses, fix efficiency before adding money. This inverts the usual sequence, where budget is set annually and efficiency is reviewed afterwards.

Pair it with a cash check. The Small Business Administration identifies undercapitalisation among the most common causes of small-business failure, and an index of 1.3 still means you are paying today for gross profit that arrives over a year. Efficient growth and affordable growth are different tests, and a business needs to pass both.