Most medical cannabis patients in the UK know what their jar costs at the pharmacy. Very few can say, in plain numbers, what their pattern costs each month, each year, or what a real tolerance break saves.
To fix that, I have put a new prototype tool live on the TRSA static site: CBPM cost and dosage calculator. It is free, runs in your browser, and does not track you.
What the CBPM cost and dosage calculator does
The CBPM cost and dosage calculator at trsa.org.uk/cbpm-prototype/ is a simple web tool for people on prescription cannabis who want hard numbers, not vibes. You enter your usual pattern and the page calculates:
- Grams per day based on grams per session and sessions per day
- Grams per month assuming a 30 day month
- Estimated monthly CBPM spend in pounds
- Estimated yearly CBPM spend if you keep the same pattern
- THC per session and per day based on the THC percentage on the label
- Rough absorbed THC per day using a simple bioavailability assumption for vape, combustion, or oral route
- Tolerance break savings for a break of X days, and what that looks like if you repeat the break four times a year
There is no signup, no account, and no analytics. It is just HTML, CSS, and JavaScript running locally in your browser.
Why launch the CBPM calculator in January
January is the month when:
- People take tolerance breaks from THC after heavy December use
- Klarna, credit cards, and pharmacy bills land at the same time
- Clinics talk about “optimising dose” without showing the financial impact
If you are already thinking about a cannabis tolerance break or trying to reduce your CBPM spend in the new year, you should be able to see what that decision is worth in pounds. The calculator makes that explicit.
Instead of guessing, you can enter your real pattern, click one button to import your monthly spend, and then ask a concrete question: “What does a 31 day tolerance break save me on my medical cannabis prescription?”
For many patients on typical UK CBPM prices, the answer is measured in hundreds of pounds, not loose change. That might be the difference between carrying prescription debt into the year or paying it down.
How to use the CBPM cost and dosage calculator
- Open the tool Visit https://trsa.org.uk/cbpm-prototype/.
- Fill in your usual pattern
- Enter the THC percentage on your product, for example 18 or 22
- Enter the price you pay per gram
- Enter grams per session, for example 0.1 g, 0.2 g, or 0.25 g
- Enter how many sessions you usually have per day
- Choose your route, for example vape, combustion, or oral
- Watch the cost section update The tool calculates grams per day, grams per month, your estimated monthly CBPM cost, and your yearly cost.
- Check the THC dosage estimate You can see the theoretical THC in the material and a rough absorbed amount based on the route you picked.
- Plan a tolerance break
- Either type your average monthly spend or click “Use calculated monthly spend”
- Enter the number of days you want to take off or significantly reduce use
- The page shows how much that break saves, and the total if you repeat it four times a year
You do not need to create a spreadsheet or understand formulas. The calculator is there to make the maths visible so you can make informed choices.
Why this lives on TRSA, not a corporate patient portal
The calculator sits on TRSA, the static companion site for The Reasonable Adjustment:
- No trackers or analytics scripts
- No third party cookie banners
- No login or patient account system that can be breached later
- Static hosting that is cheap to run and hard to quietly take offline
The data you type in your browser is not sent to me, to a clinic, or to an advertising platform. It exists for as long as you have the page open.
TRSA already hosts the PGP whistleblower tool. The CBPM tool follows the same pattern – small, focused, public interest utilities that patients and whistleblowers can use without feeding another database.
What the CBPM calculator is not
Important boundaries:
- The tool is not medical advice
- It is not a dosing recommendation engine
- It does not replace your prescriber or pharmacist
The goal is transparency, not prescribing. The formulas are deliberately simple and explained in plain language. For example, THC in the material is calculated as:
mg THC = grams × 1000 × (THC percent ÷ 100)
Bioavailability values are rough estimates so that patients can see a ballpark absorbed dose for vape, combustion, or oral routes. Any actual dosing change must be discussed with a clinician who understands CBPM and your health history.
Example questions the CBPM calculator can answer
You can use the tool to answer the kind of questions patients type into search engines and AI tools every day:
- “How do I calculate my monthly cost for a 20 percent THC CBPM flower at 0.2 g per session three times a day?”
- “How much THC am I roughly absorbing per day from my prescription cannabis if I vape 0.25 g three times daily?”
- “How much money will I save if I take a 31 day cannabis tolerance break in January on my current prescription pattern?”
- “What is my yearly spend on CBPM at my current dose and how could quarterly tolerance breaks reduce that?”
Instead of guessing, you can plug the same questions into the calculator and see the numbers directly.
Planned improvements for the CBPM cost calculator
This is a prototype release. Because people are already planning January tolerance breaks, it is better to ship something useful now and refine it than to sit on it for another six months.
Planned next steps include:
- Support for multiple products on the same prescription, for example day and night flower or a mix of flower and oil
- Better handling of patterns that vary across the week, such as “only on work days” use
- Cleaner print or export layout so you can screenshot the results for a prescriber, partner, or debt adviser
- Optional educational notes on tolerance, harm reduction, and safe tapering that keep a clear line between information and advice
If there is a specific feature that would make the CBPM cost and dosage calculator more useful for you, you can contact me through the usual Reasonable Adjustment contact page.
Quick FAQ – CBPM calculator and tolerance break tool
Is the CBPM cost and dosage calculator free to use?
Yes. The CBPM calculator at trsa.org.uk/cbpm-prototype/ is free to use and does not require a login.
Does the calculator store my CBPM data or prescription details?
No. The page runs locally in your browser. Inputs are not sent to a server and are cleared when you close the tab.
Is this an official NHS or clinic tool?
No. The calculator is an independent public interest tool created by The Reasonable Adjustment and hosted on TRSA, a static archive and tools site.
Can I use the calculator to change my dose without speaking to a clinician?
No. The calculator is only for information and budgeting. Any dosing changes should be discussed with a prescriber who understands medical cannabis and your health history.
Can this help me talk to my clinic about cost and tolerance breaks?
Yes. You can use the outputs as a starting point when you ask questions such as “What is your plan to manage tolerance and cost on this prescription pattern over the next year?”
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