Trial Cost per Conversion Calculator
What a free trial programme costs per paying customer once the trials that never convert are paid for, and how that compares with what a customer is worth.
Every trial costs something — the marketing that brought it and the infrastructure and support it used — whether or not it converts.
How the trial cost per conversion calculator works
Every trial costs something — the marketing that brought it and the infrastructure and support it used — whether or not it converts. Dividing the whole month's trial cost by the trials that became customers gives the true cost of a paying customer.
Set against the gross profit a customer brings over their lifetime, that cost becomes a ratio; three or more is the usual mark of a programme worth scaling.
Formula: cost per paying customer = trials × (acquisition + running cost per trial) ÷ (trials × conversion rate); value = price × gross margin × months retained
Worked examples
| Inputs | Cost per paying customer | Note |
|---|---|---|
| Typical self-serve trial | £191.67 | 23,000 ÷ 120 = 191.67 against 576 of value |
| Cheap trials, low conversion | £166.67 | 25,000 ÷ 150 = 166.67 against 255 |
| Sales-assisted | £633.33 | 38,000 ÷ 60 = 633.33 against 6,750 |
FAQFrequently asked questions
Why charge the non-converting trials to the customers who convert?
Because they were the price of finding those customers. A trial programme is an acquisition channel; its whole cost, divided by what it produced, is what a customer cost through it. Costing only the converting trials would understate it several-fold.
What should the running cost per trial include?
The infrastructure a trial account consumes, onboarding emails, and the share of support time trials take. For a light product it is cents; for one that provisions real resources or hand-holds users it can rival the marketing cost.
What ratio is good enough?
Three or more is the common benchmark — a customer worth at least three times their acquisition cost, with the cost recovered inside a year. Below one the programme loses money on every customer it wins.
How do I raise the ratio?
Four levers, and the calculator shows each: convert more of the trials, cut the cost per trial, keep customers longer, or charge more. The break-even conversion row tells you the rate at which the programme merely pays for itself.
Where these figures come from
- Reichheld (2003), Harvard Business Review — The One Number You Need to Grow — the paper that introduced Net Promoter Score
- Financial Reporting Council — the UK accounting regulator
Last checked: September 2026. These are the industry-standard definitions; where companies commonly disagree, the page says so.