The Cannabis Control Commission has developed regulations that will allow people over 21 years of age to purchase cannabis from dispensaries in Massachusetts. The commission is imposing limits on marijuana purchases by residents and tourists alike. With the legislation that went into effect December 15, 2016 the limits were designed to prevent possible overflow in the early stages of licensing dispensaries and keep surplus products from being diverted into the black market.

The daily purchase limits of Cannabis in Massachusetts are 28 grams of dry flower or the flower equivalent in concentrates and edibles. No more than 5 grams of concentrate or 500mg of edibles can be included in that combined total sale.

Specifically, here’s the actual law as written:

500.140: Additional Operational Requirements for Retail Sale

500.140(3)(a), “In accordance with M.G.L. c. 94G, § 7, a Marijuana Retailer shall not knowingly sell more than one ounce of Marijuana or its combined dry weight equivalent in Marijuana concentrate or Edible Marijuana Products to a retail customer per day.

1. ⁠One ounce of Marijuana flower shall be equivalent to five grams of active tetrahydrocannabinol (THC) in Marijuana concentrate, including, but not limited to, Tinctures.

2. ⁠One ounce of Marijuana flower shall be equivalent to five hundred milligrams of active tetrahydrocannabinol (THC) in Edible Marijuana Products.

3. ⁠Topicals and ointments shall not be subject to a limitation on daily sales.”

Sounds confusing huh? Well, it is, sort of. This is saying, that the cannabis commission equates 5 GRAMS of concentrates, tinctures, hash, oils, and any other high potency forms of THC products to ONE OUNCE (28g) of cannabis flower.

These limits are completely different in other legal states and use various conversion factors to determine how much you can purchase per day.

In Massachusetts, the conversion factor, or ratio is 5.6:1, flower to concentrate equivalent. So for the daily limit, we simply use 5.6 multiplied by the number of single grams of the tincture. Let’s do some stoner math and give some examples, shall we?

Let’s say Tommy comes into the store and wants to purchase various items for his birthday weekend. Some edibles, a couple of vape cartridges, some pre-rolls, and some loose bud flower, because Tommy likes also to roll big Bob Marley joints.

Here’s his purchase and how it affects his daily legal purchase allotment:

1 pack of 1906 mints -w/20 5mg pieces– 100mg (5.6)

1 Coast Chocolate bar- 100mg (5.6)

2 O.pen 500mg Vape Carts (2.8×2= 5.6)

6 No.9 Pre-roll .5g (6x.5= 3.0)

7g of High Supply Hybrid flower (7.0)

Total grams purchased in converted flower equivalent:

26.8g/28g. (5.6+5.6+2.8+2.8+3.0+7.0)

So Technically, Tommy could have squeezed in a couple more half-gram joints.

Wait a minute, HOLD ON… why does a 100mg edible chocolate bar count the same as a 1000mg (1g) concentrate? Well, It’s one of the many quirks of the cannabis industry, honestly, and indeed goes against conventional wisdom because there’s 1000mg in a gram. So why does a 100mg THC edible count the same as a 1000mg vape cart… isn’t that a tenth of a gram? Shouldn’t I be able to purchase 50 packages of 100mg chocolates, mints, or other various forms of edibles? You would think so, but, we don’t make the rules around here, and that’s just how the Massachusetts laws are set up. When you consider the math, it gets even more confusing.

These limits are supposed to be based on actual amounts of usable THC that a consumer can legally purchase. In Massachusetts, dry cannabis flower, on average, contains roughly 17.8% THC potency. So, based on milligrams, one ounce of the dry flower is 28g or 28,000mg. Of which, 17.8% of that is usable THC.. or 5000mg.

So it makes perfect sense that 5g of concentrate or 5000mg is the limit, right? Sure, if that concentrate is 100% pure THC… but in reality, they’re more like 80%, on average, of pure THC. But we won’t go there. The math makes sense and is presumably based on the assumption that a typical butane extraction from 28.4 g (1 oz.) of flower will yield 5.5 g of oil.

When it comes to edibles, here’s where it gets confusing and the math is lost. Edibles are measured in mg of THC content within the consumable “piece” or “dose” as well.  So if a 100mg THC chocolate bar is assumed to contain 100mg of THC and you can only purchase a max of 500mg of these products, why aren’t edibles being counted the same way as 5000mg of vape carts, tinctures, or wax? That’s 10x less THC. What gives? It has to do with how THC affects you and the psychoactive level of the “high” it produces. Also, based upon how it’s consumed, the temperature, or if it’s combusted and inhaled dictates how the body absorbs it. We can presume, the various commissions decided that a typical chocolate bar when orally consumed or ingested, will absorb 10x more THC than when combusted and inhaled.

When edibles are consumed the THC is metabolized by the liver, which makes them much more potent. Also, if we look at dosages, 5-10mg is a typical dose, which gives a consumer roughly 100 doses if they purchase the full 500mg allowed in a 24hr period. Some would argue that 5000mg of THC infused vape juice would yield many more “doses”, than 100, and they’d more often than not be correct. They would also be correct in saying that an ounce of 30% THC strain of Indica flower, would provide much more than 100 doses.


At face value, these seem like small deviations from relatively innocuous amounts of each product. The problem, researchers say, is that the weight of a product tells nothing about the amount of THC, the main psychoactive ingredient in cannabis used to measure potency. The amount of THC in each class of products can vary substantially. Flowers and bud material can vary from 8 percent to 34 percent THC, while concentrates can vary from 40 to 97 percent THC, based on real products sold on the legal adult-use or medical market throughout Massachusetts and all other legal states.

When it pertains to Massachusetts daily recreational marijuana purchase limits, it’s best to throw all that icky science stuff and conventional wisdom out the window, and just, for simplicity’s sake, use the “fives” rule. 1 gram of wax or oil is roughly 5 grams of flower. For edibles, it’s kind of like fives too, but instead, 100mg chocolate bars are like 5 grams of flower. Make sense? We thought it would eventually, with some funny rounding added too. Sorry Math fans, we don’t want to argue… we know, technically, there are 28.3495 grams in an ounce. But the industry uses a straight 28grams, rounded down. And the 5.3 ratios cited here, is also confounded by some fuzzy math and is actually 5.6 in practice, for calculating a daily limit total. Because well, 28 divided by 5 equals 5.6, not 5.3.