One conversion solves most of this: 1% of a gram is 10 milligrams.
Flower is labeled in percentages. Edibles are labeled in milligrams. Vape carts are labeled in both, inconsistently. They're measuring the same thing in different units, and the bridge between them is that single line. A gram of 25% THCA flower contains roughly 250 mg of THCA. A 10 mg gummy contains 10 mg. Those numbers are now comparable β with a large caveat about absorption that we'll get to, because it's the part that actually determines what you feel.
Here's the full picture: how to do the math, and why the math alone will mislead you if you stop there.
The conversion, step by step
A percentage is a fraction of the total weight. A milligram is an absolute amount. To move between them you only need the weight of the product.
Percent to milligrams: multiply the weight in grams by the percentage, then by 10.
A 3.5 gram eighth at 28% THCA:
3.5 Γ 28 Γ 10 = 980 mg of THCA in the jar.
Milligrams to percent: divide milligrams by the weight in milligrams, times 100.
A 1 gram (1,000 mg) cart containing 850 mg of cannabinoids:
850 Γ· 1000 Γ 100 = 85%.
That's it. If you want a refresher on the weights themselves β what an eighth actually is, how grams ladder up to ounces β we covered that in Cannabis Weights Explained.
The THCA adjustment
There's one correction specific to flower, and skipping it inflates your number by about 12%.
THCA isn't THC. It's the acid form, and it's a heavier molecule β it carries a carboxyl group that falls off when heated. When THCA decarboxylates into delta-9 THC, that group leaves as carbon dioxide, and the resulting THC weighs about 87.7% of what the THCA did.
So the standard conversion is:
Potential THC = THCA Γ 0.877
Our eighth from earlier, at 980 mg of THCA, has a theoretical ceiling of about 859 mg of delta-9 THC β if every molecule converted, which it won't.
This 0.877 factor is also what drives the βtotal THCβ formula labs and regulators use: total THC = delta-9 THC + (THCA Γ 0.877). It's the same arithmetic behind the federal rule change taking effect December 11, 2026, which counts THCA toward the 0.3% limit instead of ignoring it.
Where the math stops working
You now have a number of milligrams in the package. That is not the number of milligrams that reaches your bloodstream, and the gap between them is enormous and format-dependent.
Combustion loses most of it
Light a joint and a large fraction of the THC is destroyed by the flame or drifts off in sidestream smoke. Of what you inhale, some is exhaled before it's absorbed. Published bioavailability estimates for smoking land roughly in the 10β35% range, with wide individual variation based on how you inhale and hold.
So that 859 mg theoretical ceiling in an eighth? Perhaps 85 to 300 mg of it actually gets into you, spread across however many sessions the eighth lasts.
Vaporizing loses less
Vaporizing avoids combustion losses and generally lands at the upper end of that range or above. That's not a small difference β it's a meaningful reason two products with identical lab numbers can feel very different. We went through the mechanism in The Science of Vaporization vs. Combustion.
Edibles lose it differently β and change the molecule
Swallowed THC goes through the liver before reaching general circulation. First-pass metabolism knocks oral bioavailability down to roughly 4β20%, which is why the milligram number on a gummy looks so much smaller than the milligram number in a jar of flower.
But the liver also converts a substantial share of delta-9 THC into 11-hydroxy-THC, a metabolite that crosses into the brain readily and is generally considered more potent than delta-9 itself. So oral doses deliver less material, in a different and stronger form, on a much slower timeline. That combination is exactly why edibles catch people off guard even when the milligram number looks modest. The full pharmacology is in Inhalation vs. Oral Consumption.
The takeaway: 10 mg inhaled and 10 mg eaten are not comparable experiences. The unit is the same. Everything downstream of the unit is not.
Practical comparisons
With those caveats stated, here's what the arithmetic is genuinely good for.
Comparing price
This is where the math earns its keep, because cost per milligram is a real, format-internal comparison.
A 3.5 g eighth at 28% THCA = 980 mg. At $40, that's about 4.1Β’ per mg.
A 1 g cart at 85% = 850 mg. At $35, that's about 4.1Β’ per mg.
A 10-pack of 10 mg gummies = 100 mg. At $25, that's 25Β’ per mg.
Interesting result, and a common one: flower and carts often land close on raw cannabinoid cost, while edibles cost several times more per milligram β because you're paying for formulation, not just cannabinoid. Whether that's worth it depends on what you want out of the format, but at least you now know what you're paying for. Our breakdown of what separates price tiers in flower covers the other half of that question.
Sizing a first dose in an unfamiliar format
Within a format, milligrams are a reasonable guide. Across formats, use published starting points rather than converted math:
- Edibles, new user: 2.5β5 mg, then wait a full two hours before considering more.
- Inhaled, new user: one small puff, wait 15 minutes. Onset is fast enough that you can titrate in real time β that's the main advantage inhalation has.
The beginner's guide to THCA flower goes deeper on pacing a first session.
Judging whether a number is plausible
A flower COA claiming 40% THCA should raise an eyebrow. Real flower typically tests in the high teens to low thirties, and numbers above that are usually a sampling artifact β loose trichomes concentrating in the tested sample. What Is a Good THCA Percentage? explains why the highest number on the shelf is rarely the best flower on the shelf, and why terpene content predicts your experience better than the headline percentage does.
A quick reference
| Format | Typical label | Convert to mg | Rough bioavailability |
|---|---|---|---|
| Flower | % THCA | grams Γ % Γ 10 | 10β35% (smoked) |
| Concentrate | % total cannabinoids | grams Γ % Γ 10 | Higher, vaporized |
| Cart | mg or % per gram | already mg, or Γ 10 | Higher, vaporized |
| Edible | mg per piece | already mg | 4β20%, plus 11-OH conversion |
And the two formulas worth remembering:
- 1% of 1 gram = 10 mg
- Potential THC = THCA Γ 0.877
What to do with this
The arithmetic is genuinely useful for two things: comparing price across products, and sanity-checking a label that seems too good. It's much less useful for predicting how something will feel, because absorption, tolerance, terpene profile and your own body all sit between the milligram and the effect.
Use the math to shop. Use caution and a wait-and-see approach to dose. And when you're comparing a gram of flower to a gummy, remember that you're converting units, not experiences.
Chubby Smoke products are lab-tested and intended for adults 21+. This article is educational and is not legal or medical advice. These statements have not been evaluated by the FDA.
