PG carries flavor and gives you the throat hit, VG makes the clouds and tastes a little sweet, and almost every bottle of e-juice blends the two at a set ratio to balance both.
Walk into any vape shop and read the labels. Every bottle has a number like 70/30 or 50/50 stamped on it. That's the VG-to-PG ratio, and it's the single biggest factor in how a juice tastes, how much vapor it makes, and how hard it hits your throat. The hardware matters too, but the ratio is what you're picking when you grab the bottle off the shelf.
The Short Answer: What PG and VG Actually Do
PG is propylene glycol. VG is vegetable glycerin. They're both clear, slightly viscous liquids that hold the nicotine and flavoring in your e-juice. Your device heats the mix, the liquid turns into aerosol, and you inhale it.
Past that shared role, they behave very differently:
- PG is thin. It runs into a coil fast, vaporizes at a lower temperature, carries flavor molecules cleanly, and produces a sharper, more cigarette-like throat hit.
- VG is thick. It produces more visible vapor per puff, has a faint natural sweetness, and softens the throat hit.
If you've ever switched from a Juul-style pod to a sub-ohm tank and felt the throat hit disappear behind a wall of cloud, that's the ratio shifting under you. The label tells you which direction your next bottle will tilt.
The Chemistry (and Why It Matters at the Coil)
Propylene glycol is a small diol. Molecular weight is 76 g/mol, which is part of why it vaporizes easily at the temperatures vape coils actually run at. The FDA lists PG as Generally Recognized as Safe (GRAS) for food use, and the same compound shows up in asthma inhalers and theatrical fog machines. Long-term inhalation data from vape products is still limited, which is the honest answer to most "is PG safe?" questions.
Vegetable glycerin is a trihydric alcohol. Molecular weight is 92 g/mol, viscosity is roughly 30 times higher than PG at room temperature, and it carries more energy per gram during vaporization. That's why VG makes thick, dense clouds, why it strains older coils, and why pure-VG juice can struggle to wick through a tight cotton coil designed for thinner liquid.
The thermal degradation question matters here. Both PG and VG can break down into carbonyls like formaldehyde, acetaldehyde, and acrolein when overheated, and the rate climbs sharply once a coil gets pushed past its design wattage. The UK government's 2022 evidence update on vaping concluded these carbonyl levels stay well below combustible cigarette smoke when devices are used as intended, but rise meaningfully in dry-hit or chain-vape conditions. A burnt hit is the worst-case version of that chemistry, which is the reason coil priming and wattage caps exist.
Common Ratios and What They're For
Most e-liquid sold in the US sticks to a handful of standard ratios. The number on the bottle tells you almost everything about how the juice will behave.
| Ratio (VG/PG) | Vapor | Throat Hit | Flavor | Best With |
|---|---|---|---|---|
| 30/70 | Low | Strong | Very crisp | Older MTL tanks, freebase nic juice |
| 50/50 | Medium | Balanced | Strong | Pod systems, salt nic, beginner MTL |
| 60/40 | Medium-high | Moderate | Strong | Mid-power tanks and RTAs |
| 70/30 | High | Mild | Medium | Sub-ohm tanks, mesh coils |
| 80/20 to max VG | Very high | Very mild | Rounded, sweet | Cloud chasers, rebuildables |
Pod systems and disposables almost always ship with 50/50 salt nic. PG is what makes high-nicotine salt juice tolerable at 20mg or 50mg instead of brutal. Freebase juice in a sub-ohm setup usually lands at 70/30 VG/PG to keep wicking smooth and clouds dense without choking out the flavor.
For a closer look at how this maps to draw style, our MTL vs DTL vaping guide walks through which ratios pair with which inhale technique.
How Your Hardware Limits Your Ratio
The coil dictates the ratio, not the other way around. Ignore this and you get burnt hits, flooded chambers, or both.
High-PG juice in a sub-ohm coil
A 70/30 PG/VG mix in a 0.15-ohm mesh coil floods. The PG runs too thin for the wick to control, and the open airflow pulls liquid faster than the coil can vaporize it. You get a wet mouthful, some leaking down the chimney, and a harsh hit when the coil finally fires dry. Sub-ohm hardware expects VG-heavy juice for a reason.
Max-VG juice in a 1.2-ohm pod coil
The other direction is worse. Pure VG is so thick it can't wick through a tight cotton coil designed for thin liquid. You vape on a dry coil for a fraction of a second before the cotton catches up, and that's a burnt hit. Pod systems, MTL tanks, and disposables almost universally use 50/50 or 60/40 juice.
How to check before you buy
The coil packaging or device manual usually lists a recommended ratio. If it doesn't, resistance is a decent shortcut: anything 1.0 ohm and above wants 50/50 or 60/40, anything below 0.5 ohm wants 70/30 or higher VG. Our ultimate guide to vape coils covers wicking behavior and coil compatibility in more detail.
Safety, Allergies, and What the Research Says
In adults using regulated e-liquid as intended, PG and VG aerosol exposure stays far below the harm level from combustible tobacco. The Royal College of Physicians' 2024 evidence review, an update to its 2016 landmark report, kept the long-standing finding that vape aerosol harm is "unlikely to exceed 5% of the harm from smoking tobacco". The CDC's most recent guidance still flags e-cigarettes as containing potentially harmful substances, and continues to recommend non-users never start.
That isn't the same as "safe." A small minority of vapers report a PG sensitivity: dry mouth, sore throat, mild rash, occasionally hives. True allergy to PG is rare in the research, but irritation at high-PG ratios shows up in user reports often enough to be worth taking seriously. If a 50/50 juice leaves your throat raw after a day, switching to a 70/30 VG-dominant blend in compatible hardware usually clears it up.
VG-specific reactions are even less common. The compound shows up in toothpaste, hand cream, and food. Where VG does cause trouble, it's usually indirect. The extra sweetness encourages chain vaping, which dries out the mouth and gums and contributes to the "vaper's tongue" effect where flavors stop registering.
Picking the Right Ratio for You
Skip the spreadsheet. Three questions usually settle it.
What device are you using? A pod or disposable means 50/50, full stop. A sub-ohm tank means 70/30. Anything in between gets an in-between ratio. The device manual is the cheat code.
Are you chasing clouds or chasing flavor? Higher VG makes bigger clouds and softer flavor. Higher PG makes crisper flavor and a sharper throat hit. You can't get all four at maximum from one bottle.
Are you using freebase or salt nic? Salt nic almost always ships at 50/50, because the throat hit at 20mg or 50mg salt would be intolerable in a VG-dominant base. Freebase at 3-6mg in a sub-ohm setup wants the 70/30 blend.
For DIY mixers, our vape calculators cover the ratio math along with nicotine concentration. If you're still working out what mg/mL you actually need, start with the nicotine calculator before you worry about base ratios.