Small companies in the UK and the US sometimes want a clear way to think about the size of a possible bitcoin allocation. What they usually do not want is to type reserve figures into a tool that sends those figures to someone else's server.

We built a free, open-formula sizing calculator that runs in the browser. Nothing typed into it leaves the device.

The method is conservative and deliberately simple. It starts with what the business must protect, not with a target holding:

  1. Set aside a fixed number of months of operating costs, plus known obligations such as tax due, loan repayments and planned capital spend.
  2. Treat only the cash above that protected amount as excess.
  3. Cap any allocation at a chosen percentage of that excess. The board can also set an absolute hard cap.
  4. Run a stress test on the resulting figure, so a fall in the allocation is visible before any decision is recorded.

The calculator shows every step. There is no recommended allocation. The point is to make the number a deliberate, recorded choice, and then to put the chosen limits into a treasury policy for advisers to review.

The formulas and the code are public:

https://github.com/iotfinancial-code/treasury-toolkit

The live tools, including the sizing calculator, a custody questionnaire, a policy generator and a few other open-formula utilities, are here:

https://iotfinancial.net/tools/

IoT Financial is a free education site for owners, directors and their accountants at small companies in the UK and the US. The material is education, not advice. There is nothing to buy and no affiliate links.

Disclosure: we publish IoT Financial and the open-source treasury toolkit linked above.