SaaS unit economics measure what it costs to acquire a customer and how much gross profit that customer generates over time. Start with a group that first paid in the same period. Calculate acquisition cost and payback for that group. Use a separate calculation for the subscribers who were already customers when the period began.
A sales leader deciding whether to fund another campaign needs both views. An upgrade can improve growth while the next new customer takes just as long to repay their acquisition cost. In the editable cohort workbook, open Customer economics. The fictional example is in USD. Replace the inputs with one channel and period from your own records before comparing two campaigns.
First customer group: ten new subscriptions
The team attributes USD 100,000 of acquisition spending to ten new customers. Include salaries, commissions, programs and the cost of pursuing unsuccessful prospects under the same allocation policy. Put renewal and expansion work in a separate bucket. In a long sales cycle, some of the acquisition spend belongs to an earlier period. Document the lag or allocation estimate instead of shifting spend until the payback looks shorter.
| Measure | Calculation | Result |
|---|---|---|
| CAC per new customer | USD 100,000 ÷ 10 | USD 10,000 |
| Starting MRR per customer | USD 6,250 ÷ 10 | USD 625 |
| Monthly gross profit per active customer | USD 625 × 80% | USD 500 |
| Payback at the starting rate | USD 10,000 ÷ USD 500 | 20 months |
The same calculation works for the group as a whole. At the starting subscription rate and margin, the group earns USD 5,000 of gross profit per month against the USD 100,000 outlay. This is an estimate at a constant rate. To find realized payback, accumulate actual gross profit from those ten customers, month by month. Mark the first month the total reaches USD 100,000, or mark it unrecovered at the reporting date. Collections and payment terms belong in a separate cash schedule. Gross-margin-adjusted payback formula
Second customer group: the opening base
Existing customers begin the month at USD 20,000 MRR. They add USD 2,000 through upgrades, lose USD 500 through downgrades and lose USD 1,000 through cancellations. Ending MRR from those same accounts is USD 20,500. Net revenue retention (NRR) is USD 20,500 ÷ USD 20,000 = 102.5%. Keep the ten new customers out of both sides. Their USD 6,250 in starting MRR brings the total net MRR increase to USD 6,750. ChartMogul’s NRR methodology
Dividing the acquisition spend by (USD 6,750 × 80%) would produce about 18.52 months. That denominator includes an existing-customer gain of USD 500. The sales team still needs 20 months at the new customers’ starting rate. Use NRR and GRR to explain what changed in the opening base.
What to change in the workbook
Reduce the assumed gross margin from 80% to 60%. Monthly gross profit per new account falls to USD 375 and steady-rate payback rises to about 26.67 months. Restore the 80% margin, then raise assumed monthly customer churn from 2% to 4%. The starting-rate payback still reads 20 months. Expected lifetime gross profit falls because fewer customers remain to make later payments. See the LTV:CAC calculation for the assumptions and the resulting 1.25× ratio.
If your board tracks a sales efficiency or “magic number,” write down which revenue change and which quarter’s sales and marketing spend feed it. A change in total recurring revenue can include upgrades and cancellations. Compare it with the two customer groups above before using it in a hiring decision. For the forecast meeting, bring the observed renewal history, acquisition capacity and cash plan alongside the ratio. A team paying acquisition costs today needs to know whether it can fund the wait for gross profit to arrive.