How Many Grams in an Eighth of Weed? Cannabis Weight Guide
Quick answer: An eighth of weed is 3.5 grams. That’s one eighth of an ounce, and an ounce is 28.35 grams, so the exact figure is 3.54 grams. Dispensaries round it to 3.5 g, which is the weight printed on almost every eighth you’ll buy.
Key takeaways
- 1 eighth (1/8 oz) = 3.5 grams
- 1 quarter (1/4 oz) = 7 grams
- 1 half (1/2 oz) = 14 grams
- 1 ounce = 28 grams (28.35 exactly)
- 1 pound = 16 ounces, or about 454 grams
- An average joint holds about 0.32 grams, so an eighth rolls roughly 11 joints.
How many grams are in an eighth?
An eighth of an ounce is 3.5 grams. The math comes from the official conversion: one ounce equals 28.35 grams, and 28.35 divided by 8 is 3.54. Cannabis menus drop the extra 0.04 g and list eighths as 3.5 g.
You’ll also see it written as an 8th, 1/8, 1/8th of an ounce or 1/8 oz. They all mean the same weight.
Cannabis weight chart: grams to ounces
| Name | Fraction of an ounce | Grams (dispensary) | Grams (exact) |
|---|---|---|---|
| Gram | about 1/28 | 1 g | 1 g |
| Eighth | 1/8 oz | 3.5 g | 3.54 g |
| Quarter | 1/4 oz | 7 g | 7.09 g |
| Half (half ounce) | 1/2 oz | 14 g | 14.17 g |
| Ounce (zip, O) | 1 oz | 28 g | 28.35 g |
| Pound (QP is a quarter pound) | 16 oz | 448 g | 453.6 g |
The “dispensary” column is how weights are usually sold. Because each step rounds down a little, an ounce bought as eight separate eighths (28 g) can come out slightly lighter than a true ounce (28.35 g).
Why is cannabis sold in ounces and grams at the same time?
US commerce has always used ounces and pounds, and cannabis simply inherited them. Smaller amounts are easier to weigh and price in grams, so the market ended up with a mix: you buy an “eighth” or an “ounce” by name, but the package and the scale show grams.
The gram is the unit that matters most for shoppers. It’s what you need for comparing prices, and for accurate dosing when you’re making edibles or measuring concentrates.
How many joints can you roll from an eighth or an ounce?
A study of marijuana purchases in the US estimated that the average joint contains 0.32 grams. Using that figure:
- An eighth (3.5 g) makes about 11 joints.
- A quarter (7 g) makes about 22 joints.
- An ounce (28 g) makes about 87 joints.
If you roll fatter 0.5 g joints, divide by two instead: about 7 per eighth and 56 per ounce.
How do you work out the price per gram?
Divide the price by the grams. A $35 eighth is $35 ÷ 3.5 = $10 per gram. A $200 ounce is $200 ÷ 28 = about $7.14 per gram. Price per gram is the only fair way to compare sizes and shops, and it shows when a bulk deal actually saves you money. For more ways to stretch your budget, see our guide to cannabis on a budget.
Does weight tell you everything about quality?
No. Two eighths can weigh the same and smoke completely differently. Look for well-cured buds with a strong aroma and plenty of trichomes, the resin glands that hold cannabinoids and terpenes. A fresh eighth of a strain you like beats a cheap, dry ounce. If you’re trying new strains, an eighth is the right size to test one without overcommitting.
Tips for buying the right weight
- Check the scale. Licensed shops use certified scales, and you can ask to see your flower weighed.
- Compare per gram, not per package. Bigger isn’t always cheaper.
- Buy small when you’re experimenting. Eighths keep flower fresh and let you try more strains.
- Use a pocket scale at home. It makes rolling, dosing and recipe work far more accurate.
FAQ
Is an eighth 3.5 or 3.54 grams?
Both. Mathematically it’s 3.54 g. In practice, dispensaries sell and label it as 3.5 g.
How many eighths are in an ounce?
Eight. That’s where the name comes from: each one is 1/8 of an ounce.
Is a quarter 7 grams?
Yes. A quarter ounce is two eighths, or 7 grams (7.09 g exactly).
How many grams are in a pound of weed?
About 454 grams (453.6 g exactly). Sold as 16 dispensary ounces, it works out to 448 g.
Is “an 8th” the same as “1/8 oz”?
Yes. 8th, eighth, 1/8, 1/8th and 1/8 oz all mean 3.5 grams.
Sources
- NIST Office of Weights and Measures, Approximate Conversions from U.S. Customary Measures to Metric.
- Ridgeway G, Kilmer B. Bayesian inference for the distribution of grams of marijuana in a joint. Drug and Alcohol Dependence, 2016. Summary via ScienceDaily.
Related reading: Dank Weed: Good or Bad? The Truth Behind this Weed Slang and Monthly Subscription Box Deals for Cannabis Lovers.
The information contained in this blog post is for informational purposes only and is not intended as a substitute for medical advice, diagnosis, or treatment. Read our full disclaimer.
