A 1 gram cartridge contains approximately 1 ml of oil. The two numbers are nearly identical because cannabis distillate has a density very close to water, hovering right around 1.0 to 1.05 grams per milliliter at room temperature. So when you see a cartridge labeled “1g,” you’re looking at roughly 1 ml of liquid inside.
Why 1 Gram and 1 ml Are Nearly the Same
Grams measure weight, and milliliters measure volume. They only line up perfectly when a liquid has the same density as water (exactly 1.0 g/ml). Cannabis distillate is extremely close to that mark. Lab measurements of THC distillate at around 85% purity put its density at approximately 1.032 g/ml at room temperature. That means 1 gram of distillate occupies about 0.97 ml, a difference so small it’s essentially negligible for practical purposes.
The density shifts slightly with temperature. Warmer oil becomes less dense, so if a cartridge has been sitting in a hot car, the same gram of oil takes up fractionally more space. At 60°C (140°F), distillate density drops to about 1.008 g/ml, and at 90°C it dips just below 1.0. None of these variations change the user experience in any meaningful way, but they explain why the oil level in your cartridge can look slightly different depending on conditions.
How Cartridges Are Actually Sized
The cartridge hardware itself is designed around milliliters, not grams. Major manufacturers like CCELL build their standard 510-thread cartridges in two sizes: 0.5 ml and 1 ml tank capacity. When a brand fills a “1 gram” cartridge, they’re putting product into a 1 ml tank. The labeling convention uses grams because cannabis is regulated and sold by weight, but the physical container is engineered to hold 1 ml of liquid.
This is worth knowing because it means the cartridge tank isn’t oversized with extra headroom. A 1 ml tank filled with 1 gram of distillate will look full, with just the tiniest bit of space at the top. If your new cartridge looks like it has a noticeable air bubble or seems underfilled, that’s not a gram-to-ml conversion issue. It more likely means the wick has already absorbed some oil, or the cartridge wasn’t filled completely.
When the Conversion Gets Less Exact
The near-perfect 1:1 ratio applies specifically to distillate, which is the thick, honey-like oil used in most cartridges. If a cartridge contains a different type of extract, the density can vary more. Live resin, for example, often includes a broader mix of plant compounds and terpenes that can shift the density slightly in either direction. CO2 oil and other formulations blended with thinning agents will typically be a bit lighter than pure distillate, meaning 1 gram could take up slightly more than 1 ml.
In practice, these differences rarely exceed 5%. For any standard cannabis cartridge you’d buy at a dispensary, treating 1 gram as 1 ml is accurate enough for any comparison you’d need to make, whether you’re estimating how many puffs you have left or comparing prices between gram and half-gram options.
Half Gram Cartridges Follow the Same Math
The same logic scales down. A 0.5 gram cartridge holds approximately 0.5 ml of oil in a 0.5 ml tank. If you’re trying to figure out whether a half gram cart is a better deal than a full gram, the conversion is straightforward: two half gram cartridges equal one full gram cartridge in terms of actual oil volume. The only difference is that you’re paying for two pieces of hardware instead of one, which is why full gram cartridges are almost always cheaper per gram.