If you track your medical cannabis use, there is one number that matters more than almost any other: your burn rate. It tells you how quickly you are using your prescription, whether you are on track, and when you are likely to run out.
Here is everything you need to know about burn rate — what it is, how to calculate it, and why it is the most practical metric for day-to-day stock management.
What is burn rate?
Burn rate is your average daily consumption over a given period. It is expressed in grams per day — for example, 0.4 g/day means you use about 0.4 grams each day on average. The period you choose matters: a 7-day burn rate reflects your recent usage (good for checking if you have changed habits), while a 30-day burn rate gives a longer-term average (better for planning).
Your burn rate is not a target. It is a measurement — a reflection of what you actually use, not what you think you should be using. That distinction is important: burn rate helps you understand your patterns, not judge them.
Why burn rate matters
There are three practical uses for knowing your burn rate:
1. Avoiding running out. Your burn rate, combined with your remaining stock, tells you how many days of medication you have left. If your prescription provides 30 grams per month and your burn rate is 1.2 g/day, you have about 25 days of stock — meaning you will run out before the month ends unless you adjust.
2. Clinic conversations. When your clinician asks how you are getting on with your prescription, "my burn rate is about 0.5 g/day and has been steady for the last month" is a much stronger answer than "I think I am using about the right amount." Data makes these conversations more productive.
3. Spotting changes over time. Is your consumption increasing, decreasing, or steady? A burn rate trend over weeks and months reveals patterns that are hard to see day to day. If it is creeping up, you can address it before it becomes a problem. If it is dropping, that is useful information for your next review.
How to calculate burn rate
The formula is simple:
Burn rate = total amount used / number of days
For example, if you used 4.2 grams over the last 7 days, your burn rate is 0.6 g/day. If you used 16 grams over the last 30 days, your burn rate is about 0.53 g/day.
The challenge is doing this by hand. You need to add up every dose across every product — and if you miss a day or an entry, the calculation is off. This is why most patients who track manually give up on burn rate after a week or two: the maths is tedious, and the result is only as good as the data.
What affects your burn rate?
Several factors can change your burn rate, and being aware of them helps you interpret the number:
- Product changes. A new strain or format (flower vs oil) may have a different consumption pattern.
- Symptoms. If your symptoms are worse than usual, your consumption may increase temporarily.
- Routine changes. Weekends, holidays, or changes in work schedule can shift when and how much you use.
- Method changes. Vaping, oils, and edibles all have different consumption patterns and effective amounts.
None of these are problems — they are just data. Knowing what influences your burn rate helps you interpret it rather than react to a single number out of context.
How Grams Left handles burn rate
In Grams Left, your burn rate is calculated automatically with every dose you log. It updates in real time, so you always know your current pace. No formulas, no adding up entries by hand, no wondering if you missed a day. The app also shows your burn rate trend over time, so you can see whether it is steady, rising, or falling.
The core tracker, including burn rate and prescription countdown, is free forever, with no card required.
Treat your burn rate as a measurement rather than a verdict. Tracked honestly over a few weeks, it tells you where you actually stand and gives your clinician something concrete to work with.