The only division that makes two offers comparable
Two products at the same price can differ by a factor of several in what they actually deliver. Price per bottle compares packaging. Price per gram compares mass. Neither compares the thing anyone is buying.
One division fixes it: the price divided by the milligrams of the principal compound the product contains. It takes a moment, it works across every format, and it regularly reverses which of two products looks better.
This page covers how the calculation works, where the numbers come from, what makes it go wrong, why sellers rarely present it, and what it reveals when applied across a catalogue.
⚠️ Scope. This page describes a process and what can be verified from documents. It does not describe what a product does to a person, gives no amounts, and does not replace a healthcare professional.
🔴 The calculation
The formula
The total price divided by the total milligrams of the principal compound in the container. The result is a price per milligram.
Where the price comes from
The listing, including delivery where you are comparing total cost. Delivery can dominate on small purchases.
Where the milligrams come from
The certificate, ideally. The label where the certificate is unavailable, with the caveats described below.
What you get
A single number that compares directly across bottles, tinctures, capsules, flower and isolate. That universality is the point.
Why price per gram fails
Across concentrations
Two oils of the same volume at different concentrations contain different quantities. Comparing the bottles compares glass.
Across formats
A gram of flower and a gram of extract are not comparable in any sense that matters. The compound content differs by an order of magnitude.
Across pack sizes
Larger containers are generally cheaper per unit, which price per gram captures and which tells you nothing about the compound.
What it does capture
Mass. That is useful for shipping and for very little else.
Getting the milligram figure right
From a certificate
The content figure for the batch, per unit or per container. It is the measured value and it is what you want.
The conversion trap
If the certificate reports an acid form and a neutral form, the total must apply the conversion factor rather than adding the rows. A plain sum overstates the content.
From a label
The stated content, which may or may not be the converted total. It is a starting point rather than a measurement.
The check
Whether the label figure matches the certificate. Where they diverge, the certificate is the measurement.
🔴 Where the calculation goes wrong
Percentage without a basis
A percentage of what, measured how. Without that it cannot be converted into milligrams and it compares nothing.
Total cannabinoids
Some products state a total across all compounds rather than the principal one. That is a different number and it inflates the comparison.
Per-serving figures
Where a serving is defined by the seller, and the definition varies. Convert everything to the whole container before dividing.
Missing volumes
A concentration without a volume, or a volume without a concentration. Both appear and neither supports the calculation.
A worked comparison
Two oils
One at a higher concentration in a smaller bottle, one at a lower concentration in a larger bottle, at similar prices.
The intuition
The larger bottle looks like better value, because it is more product for the money.
The calculation
Multiply concentration by volume for each to get total milligrams, then divide each price by its total.
What frequently emerges
The smaller, more concentrated bottle wins, because concentration scales the content faster than volume scales the price.
Comparing across formats
Oil against capsules
Capsules state a content per unit and a count. Multiply and divide. They are frequently more expensive per milligram for the convenience of pre-measurement.
Oil against isolate
Isolate is generally the cheapest per milligram by a wide margin, before accounting for the scale and the work.
Flower against extract
Flower content is stated as a percentage of mass, which converts directly to milligrams per gram. The comparison is then straightforward.
What the comparison exposes
That format premiums are large, and that they buy convenience rather than compound.
What the number does not tell you
Quality
Two products at the same price per milligram can differ in every other respect: contaminants, provenance, freshness and formulation.
Suitability
Nothing about a price comparison addresses whether a product is right for anyone. That question is not ours.
Whether the content is real
The calculation assumes the stated figure is accurate. The certificate is what supports that assumption.
The full cost
Delivery, minimum orders and the practical shelf life of a large container all affect what you actually spend.
Why sellers rarely show it
It invites comparison
A number that compares directly across catalogues is a number that makes shopping around easy.
It exposes format premiums
The gap between an isolate and a finished product, expressed per milligram, is uncomfortable to display.
It is not required
Unit pricing rules apply to quantity measures such as volume and mass, not to the content of an active constituent.
Who does show it
A minority, generally the ones whose numbers are favourable. Its presence is a mild positive signal.
The delivery question
Why it matters
On small purchases delivery can be a substantial fraction of the total, and it does not scale with content.
How to include it
Add it to the price before dividing. It is the total cost that matters rather than the listed one.
What that changes
Small purchases look considerably worse and large ones considerably better. Free delivery thresholds distort this heavily.
The honest comparison
Total cost delivered, divided by total milligrams. Anything else compares an incomplete price.
The shelf life question
Why a large container can be false economy
If a product degrades before it is used, the effective price per milligram is higher than the calculation suggests.
The relevant timescale
Months for aromatic quality, longer for the principal compound. It depends on the format and the storage.
What to factor in
How long the container will realistically last at your rate of use, against how long it keeps well.
The practical rule
Buy what you will use within a few months. Beyond that the arithmetic advantage of bulk erodes.
What to do with the result
Rank the shortlist
Convert every candidate to a price per milligram and sort. It takes minutes and it usually reorders the list.
Then apply everything else
Contaminant panels, batch matching, freshness, seller documentation. The cheapest is not automatically the choice.
What the number is for
Eliminating products that are expensive for no reason you can identify. It narrows rather than decides.
What frequently survives
A mid-priced product with complete documentation, rather than either extreme. That is the usual outcome and it is a reasonable one.
The presentation tricks the number defeats
The round bottle price
A price chosen because it looks like a category rather than because it reflects content. Two bottles at the same round number can differ substantially inside.
The concentration percentage
Prominent on the label, meaningless without the volume, and the two are rarely presented with equal weight.
The large pack
More product for a slightly higher price, which is genuine value only if the content scales with the volume. Sometimes it does not.
The bundle
Several products at a combined price, where at least one is priced generously. Unbundling and calculating each separately is the only way to see it.
Where the calculation is hardest
Flower
Content is a percentage of mass, so a gram at ten per cent holds a hundred milligrams. Straightforward once you have done it once.
Cosmetics
Content is stated per container and the comparison is genuinely difficult, because how much is used per application varies enormously.
Edibles
Frequently stated per piece, which works, and sometimes per pack without a count, which does not.
Vaping products
Content per cartridge, where stated. Many are not, and a cartridge with no content figure cannot be compared at all.
What a good listing contains
The concentration
Stated clearly, with its basis.
The volume or count
Alongside it, with equal prominence.
The total content
Milligrams in the container, stated directly. It is the single most useful thing a listing can include.
The certificate
Linked, batch-matched, and current. Without it the other three are claims.
Why this number is fair to sellers too
It rewards concentration
A well-formulated product at a sensible concentration compares well. The calculation does not favour cheapness.
It exposes only unexplained premiums
A product costing more per milligram with better documentation, better panels and fresher material has a reason. The number invites the question rather than answering it.
What it removes
The ability to compete on packaging alone. That is not a loss to any seller doing serious work.
Who dislikes it
Operations whose pricing rests on presentation. Their reluctance is itself informative.
The record worth keeping
What to note
For each purchase: the price, the delivered total, the content figure, the resulting price per milligram, and the date.
Why it accumulates value
After a few purchases you have your own reference range, which is worth more than any published comparison.
What it reveals over time
Which sellers price consistently, which drift, and where the genuine outliers are in both directions.
What it costs
A line in the same notebook that holds the batch codes. The two records serve each other.
What the number cannot rescue
A product with no certificate
If the content figure is unverified, the calculation divides a price by a claim. The result looks precise and rests on nothing.
A product whose batch code does not match
The same problem in a subtler form. A certificate for a different batch describes different material, however good the figure looks.
A product that arrived degraded
The content on the certificate was measured at the analysis date. Material that has sat for a year is not what was measured.
The order that follows
Verify the figure first, then divide. A price per milligram built on an unchecked number is worse than no calculation, because it feels like diligence.
Where the exercise usually lands
Not on the cheapest
Products at the bottom of the range frequently have thin documentation, and the calculation flatters them precisely because nothing was spent on testing.
Not on the most expensive
Those tend to carry a positioning premium that the arithmetic exposes without explaining.
On something in between
A product priced sensibly per milligram, with panels covered and a batch code that matches. It is a dull conclusion and it is the usual one.
Why that is reassuring
Because it means the calculation is doing what it should: eliminating the extremes for identifiable reasons, and leaving the choice to the documentation.
A short glossary
Price per milligram
Total cost divided by the total quantity of the principal compound, which is the only figure comparable across formats.
Converted total
The neutral form plus the acid form multiplied by its conversion factor. A plain sum of the two rows overstates content.
Unit pricing
The requirement to display price per standard quantity, which applies to volume and mass rather than to active content.
Total cannabinoids
A figure summing every compound present, which is not the same as the principal compound and inflates a comparison.
Effective price
Price per milligram adjusted for delivery and for what will realistically be used before the product degrades.
The five checks that apply to any product
The batch certificate
Request it with the number printed on the packaging. A general document for the product line does not cover this batch, and those differences are exactly what it should record.
Total THC
Delta-9-THC plus THCA multiplied by 0.877, because THCA becomes THC under heat and the limit applies to the sum, not to either value alone.
Price per milligram
A division, not an opinion. The only figure that makes two products comparable, whatever the format, process and pack size.
The claims
Without an authorisation number in the EU Register these are assertions, not data — and for cannabidiol that register contains no authorised entry to this day.
The seller’s details
Company name, address and contact. Without them there is also no counterparty to turn to if something turns out to be wrong.
How this connects to the rest
With the certificate
It supplies the milligram figure, and it is where the conversion factor either was or was not applied.
With the spectrum terms
The calculation is what reveals whether a category premium reflects anything measurable.
With isolates
The format where the arithmetic is most favourable and most often not acted upon.
With expensive not meaning good
This is the number that separates a price from a justification for it.
What this is for in practice
Before any purchase
Convert the shortlist to price per milligram. It takes minutes and it reorders most comparisons.
Include delivery
Total cost delivered, divided by total content. Anything else compares an incomplete price.
Check the conversion
If the certificate has two rows, make sure the total applied the factor rather than adding them.
Then look at everything else
The number narrows a field. Documentation, panels and freshness decide within it.
Frequently asked questions
Why not compare price per gram? Because it compares mass rather than content. Two products of the same mass can differ several-fold in what they contain.
Where do I get the milligram figure? The certificate, ideally, for the specific batch. The label is a starting point and may not be the converted total.
What is the conversion trap? A certificate reporting an acid form and a neutral form. The total must apply the conversion factor; adding the rows overstates content.
Does a percentage work? Only with a stated basis. A percentage of what, measured how. Without that it cannot be converted to milligrams.
Should delivery be included? Yes, where you are comparing total outlay. On small purchases it can be a substantial share of the cost.
Does the cheapest per milligram win? No. It narrows the field. Panels, batch matching, freshness and documentation decide within it.
Why do sellers not show this? Because it makes cross-catalogue comparison easy and exposes format premiums. Unit pricing rules do not require it.
Does it work across formats? Yes, which is the whole point. Oil, capsules, flower and isolate all reduce to the same number.
What about total cannabinoids? A different figure, summing everything present. Using it inflates the comparison against products quoting the principal compound.
Is a large container better value? Per milligram usually, and only if you use it before it degrades. Buy what will be used within a few months.
What we check and what we do not
We check what can be checked from documents: official registers, declared contents, certificates of analysis, arithmetic. We test no products, rank nothing, and assert no effects.
This is the single most useful thing anyone can do before buying in this category, it takes about two minutes, and almost nobody does it. The reason is straightforward: nothing on any product page invites it, and the arithmetic has to be assembled from two different documents.
It is also the check that most often changes an answer. Bottle prices, pack sizes and percentages are all designed to be compared favourably; a price per milligram is designed to be compared honestly, and those are not the same thing.