How Much Is an Eighth of Weed? Weights, Grams and the Math

An eighth of weed is 3.5 grams, sold as one eighth of an ounce. Strictly, an eighth of an ounce is about 3.54 grams, so menus round down to the friendlier 3.5. A quarter is 7 grams, a half ounce is 14 grams, and a full ounce is 28 grams on the menu, or about 28.35 grams on the math. Everything below is arithmetic you can check yourself.

Cannabis shopping is a place where people buy by weight and often nobody shows you a scale. A little fluency pays off: you stop overpaying for the bigger tier by accident, you can tell whether a price is actually a deal, and you know how many joints you are really buying.

Weed weight chart: gram, eighth, quarter, half and ounce

The international avoirdupois ounce is defined as exactly 28.349523125 grams, and there are 16 of them in a pound (see the definition of the ounce). Every figure in the last column is that number multiplied or divided; the menu column uses the 28 g convention. The middle column is the shorthand shops tend to use; the right column is the exact conversion.

Notice what the rounding does. A menu eighth of 3.5 g is about 1.2 percent lighter than a true eighth of an ounce. That is a convention, not a rip-off, but it is why you will see the same product listed as 3.5 g in one place and 3.54 g in another.

How many grams are in an eighth of weed, and how many eighths are in an ounce?

3.5 grams in an eighth, and eight eighths in an ounce, because 28 divided by 3.5 is exactly 8. A quarter is two eighths, a half ounce is four. If you ever lose track, start from the gram figure: multiply the eighth by 2, 4 and 8 and you will land on 7, 14 and 28.

How many joints are in an eighth?

It depends on what you call a joint, because that is entirely up to the roller. At half a gram each, an eighth makes 7 joints. At a full gram each, it makes 3.5. If you roll big, you get fewer; if you roll skinny, you get more. If you want help with the rolling part, see our guide to how to roll a joint; if you would rather not roll at all, the vaporizer guide covers the option where you do not roll anything at all.

How to work out price per gram (and when the bigger size is worth it)

Divide the price by the grams. That is the whole formula. Here it is with made-up numbers, purely to show the math: if an eighth cost $35, that is $10.00 per gram. If a quarter cost $60, that is $8.57 per gram, and if an ounce cost $190, it is about $6.79 per gram. Your local prices will be different, so plug in the real ones.

The bigger size is only a better deal if you will actually use it while it is fresh, and if you are not already stacking up a tolerance. If you find yourself buying more and enjoying it less, you may want a break from using for a while, and our guide to tolerance breaks explains how to take one without drama.

Can you tell the weight just by looking?

No. Bud density varies, so the same 3.5 grams can fill a small jar or a big one. If the weight matters to you, trust the label on a sealed package and, when you are measuring at home, use a small digital scale. Check the scale against something of known weight if you want to be thorough. A 0.1 g shortfall on an eighth is about 2.9 percent. Check that your scale is accurate to 0.1 g before deciding a bag is short, and note a pattern of short bags.

Do the same sizes apply to edibles and vapes?

Not exactly. Edibles list THC in milligrams, not by the weight of the food, and a package total is not a serving. Our edible mg calculator guide walks through the dose math, and edibles 101 covers the habits that keep it sensible.

Grams to ounces and back: the quick conversion

To go from grams to ounces, divide by 28.35. To go from ounces to grams, multiply by 28.35. A few worked examples so you can sanity-check a listing: 7 grams is about 0.25 ounces, 10 grams is about 0.35 ounces, 50 grams is about 1.76 ounces and 100 grams is about 3.53 ounces. If a seller quotes ounces and grams that do not line up with those ratios, one of the numbers is off.

How long will an eighth last?

Divide the grams you have by the grams you use per day. With made-up numbers again: someone who uses a quarter of a gram a day would take 14 days to finish an eighth and 28 days to finish a quarter. Plug in your own habit, and be honest about it, because the best use of this math is spotting that the “savings” from buying in bulk assume you will finish what you buy.

Legal limits and what to buy first

Possession limits vary by place and sometimes by product type, so check the official page for your state or country before you carry or buy anything. Purchase and possession are only legal where cannabis is legal for you.

If you are working out what to put in your first eighth, the best weed strains list is a decent place to start, and a smaller size lets you try something before committing to a whole ounce.