The three blocks
Pick one AI use case. Fill in the three blocks in pounds. Everything is monthly except the one-off costs.
| Block | What goes in |
|---|---|
| 1. Costs | One-off: set-up, integration, training and your own people's time. Ongoing per month: licences, usage charges, support and the time staff spend checking AI output. |
| 2. Benefits | Per month: hours saved, rework and errors avoided, and extra revenue only if you can measure it. |
| 3. Results | Three sums that tell you whether it pays and how fast. |
The three sums
- Net monthly benefit. Total monthly benefit minus total ongoing cost. If it is zero or below, the project does not pay as planned.
- Payback. Total one-off cost divided by net monthly benefit. The number of months until the set-up cost is earned back.
- First-year return. Net monthly benefit times 12, minus the one-off cost, divided by the one-off cost, times 100. 100% means you doubled it.
Want a quick estimate first? Try the free AI ROI calculator, then use the worksheet for the real business case.
Be honest with your numbers
- Count review time. Someone has to check what the AI produces. Those hours are a cost, every month.
- Use loaded cost, not salary. Add employer costs and overheads, then divide by the hours a person actually works in a year.
- Only count hours saved if the time goes somewhere useful. Name where the time goes.
- Run a low case. Cut your benefits by about a third. If it only works on the best case, it is a bet, not a plan.
- Leave out revenue you cannot measure. "Happier customers" goes in the notes, not the sum.
- Measure before you start. Time the task for two weeks now, so you can prove the saving later.
Included: a worked example of a fictional 120-person business using AI to draft customer email replies, with every step of the sums shown.
Questions
What is loaded hourly cost?
Salary plus employer costs and overheads, divided by the hours a person actually works in a year. Ask your finance team for the figure they use.
Should we include time saved if nobody leaves?
Only if the freed-up time goes somewhere useful and you can name where. Otherwise it is not a saving.
What is a low case?
Your benefits cut by about a third. If the project still pays, it is a sound plan. If not, it is a bet.
How is this different from the ROI calculator?
The calculator gives a quick estimate in a minute. The worksheet builds the full business case with real quotes, timesheets and a low case.