How your calculator data is used
Last updated 19 October 2026. This policy covers the calculator only. Everything else is in the privacy notice.
The short version. The calculator is free. In return, when you save, open or print a case, Dewhurst.tech keeps an anonymised copy of its figures. We use those copies to follow trends - which kinds of case people build, and how the costs and savings tend to fall - and, now and then, to show combined, anonymised trends in a talk. We don't keep your name, your organisation or anything you typed about the case, unless you separately ask us to contact you. The email that brings each copy also shows your device's internet address, as explained below.
What is kept, and what isn't
Kept - the anonymised copy
- The figures on each standard line: cost, hours and whether it is one-off or yearly
- Your assumptions: currency, day cost, hours per day, time horizon, discount rate
- The results: saving, hours freed, one-off investment, payback
- Which example you started from, if any, and whether you changed it
- The month the case was saved, and a random case number so repeat saves count once
Never kept in the anonymised copy
- Your name, organisation, email or phone
- The name, description or scope you gave the case
- The names of any lines you added yourself (they are kept only as "custom line")
- Your location, beyond the currency you chose and the internet address explained below
- Anything from the saved file other than the figures above
How we may use it
- To follow trends - for example, which areas of cost are most often left out, or how payback periods tend to spread.
- To show combined trends in a talk or article - only as totals, averages or ranges drawn from at least ten separate cases, so that no single case can be picked out.
- To improve the calculator.
How we will never use it
- It is never sold, and never shared with a third party for their own use.
- No single case is ever shown, quoted or described, even anonymously.
- We never try to work out who a case belongs to.
- It is never used to market to you. Without the contact box ticked, we couldn't: we don't know who you are.
- It is never used as, or turned into, a price or a benchmark for any supplier.
If you ask us to contact you
The second tick-box is optional. If you tick it, your name, organisation, email (and phone, if you give it) and the case's name and description are sent with the copy, so we can talk the case through with you. We use them only for that conversation: no mailing list and no follow-up sequence. You can ask us to delete them at any time, and they are deleted after two years if there is no live conversation.
Our basis for keeping it
| What | Basis |
|---|---|
| The anonymised copy | It contains no personal data. Keeping it is part of the terms on which the calculator is free, and you agree to those terms when you tick the first box. |
| Your contact details, if you ask to be contacted | Your consent (UK GDPR), which you can withdraw at any time by emailing steve@dewhurst.tech. |
| Your device's internet address, on the email that brings each copy | Legitimate interests (UK GDPR) - keeping the service secure and free of spam. |
Sending the copy to us, like loading any web page, involves your device's internet address. Web3Forms adds that address to the email that carries the copy, so it arrives in our mailbox with it. We don't use it to work out who you are, and it never goes into the trend figures. Web3Forms may also pass it to a spam-checking service.
How long it is kept, and where
Anonymised copies are kept for as long as they are useful for trends, and reviewed every year. Each copy is sent by email to Dewhurst.tech's own Microsoft 365 mailbox, and held there. It is passed on by Web3Forms, a form-forwarding service. Web3Forms' own terms allow it to keep submissions for up to three years.
Questions
Email steve@dewhurst.tech. Dewhurst.tech Ltd, registered in England & Wales, company number 17373526. Registered office: 71-75 Shelton Street, Covent Garden, London WC2H 9JQ.