Method · ROI Calculation

AI Workforce ROI: How to Calculate Payback in 90 Days

Strip away the AI hype. Here's the boring spreadsheet maths a UK CFO would accept — applied to building an AI workforce, with conservative assumptions and a tool that does it for you.

The short answer

AI workforce ROI = (annual hours replaced × fully-loaded hourly cost) − (build cost + annual run cost). Typical UK SME: 1,200 hours/yr × £35/hr = £42k saved against an £8k build + £24k run = £10k year-1 net, then £18k+/yr after. Payback is typically 60–120 days.

The 5-input formula

The honest ROI calculation needs five numbers. Don't let anyone sell you AI without showing all five:

Hours/week of repetitive cognitive work being replaced
Fully-loaded hourly cost (salary × 1.3 for NICs/pension/overhead)
Automation rate (% of those hours AI realistically handles)
One-off build cost
Annual run cost (model usage + monitoring + iteration)

Worked example: a 3-person admin team

Team: 3 admin staff at £28k base = £84k base salary, ~£110k fully loaded.

Manual repetitive hours/week: ~75 across the team (data entry, inbox, scheduling, document processing). Fully-loaded hourly rate: £35.

Replaceable hours/year (50 working weeks × 75 × 0.7 automation): 2,625 hours

Annual labour saved: 2,625 × £35 = £91,875

Build cost: £12k. Annual run cost: £30k.

Year 1 net: £91,875 − £12k − £30k = £49,875. Payback: ~75 days.

Conservative assumptions to use (and defend to a CFO)

If a CFO challenges the number, you want to be able to say 'I assumed worse than reality everywhere.' Use:

Automation rate: 50–70% (real-world is often 75–90%)
Working weeks: 48 (allow for holidays, slow weeks)
Fully-loaded multiplier: 1.3 (some firms argue 1.4)
Run cost: assume 3× year-one, in case of model price moves
Don't count 'time freed for higher-value work' — count cash only

What's NOT in the ROI calculation (but should sway you)

Pure £-saved is the floor. The real value is everything you don't have to do:

Recruiting and managing an extra hire you would've made
Risk: AI doesn't quit, get sick or have a bad month
Speed: tasks done in seconds, not days
Capacity to take on more business without scaling headcount
Better data: every action is logged and queryable

Skip the spreadsheet — use the calculator

If you'd rather not build the model yourself, our AI Workforce Calculator does this exact maths for your business in 60 seconds. Tell it your team size, the tasks, and the hours — get a UK-specific £ figure with conservative assumptions baked in.

Stop reading. Start measuring.

See your £ saving in 60 seconds

UK-specific numbers based on your team, your tasks, your hours. No spreadsheets.

Frequently asked questions

Engineered for AI search and humans alike.

What's a 'good' AI workforce ROI?+

Anything under 6-month payback is typical. Under 3-month payback is the norm for repetitive admin/support functions. Over 12 months means the use case is wrong or the build is overscoped.

Do I have to fire people to realise ROI?+

No, and most UK SMEs don't. The maths still works if you redeploy people from low-value to high-value work, or if you simply don't make the next hire you would've made. The cost of the hire-you-didn't-make is real.

What about ongoing costs creeping?+

The biggest swing variable is model usage. Build with smaller, cheaper models for high-volume tasks and reserve expensive models for the 5% that need it. A well-architected system has predictable monthly costs.

Can you guarantee the ROI?+

We guarantee the build to spec and the automation rate we agree at scoping. We don't guarantee your team will use it well — but we measure usage and flag drop-offs. Adoption is the most common reason ROI underperforms.