14mm vs 18mm Bong: Explaining the Difference and How to Tell Which You Have

The 14mm vs 18mm bong question sounds like it should be about performance - bigger joint, bigger rips, right? Not quite. The real difference between these two sizes comes down to accessory compatibility: which bowls, downstems, and ash catchers actually fit your piece. 

We carry a wide range of glass bongs in both joint sizes, all hand-picked and inspected by our team here in Southern California. But grab the wrong size bowl replacement, and you'll find out the hard way why this stuff matters. 

Learn how to tell if your bong is 14mm or 18mm below.

14mm vs 18mm Bong (Fast Facts)

14mm vs 18mm Bong: What Are We Really Talking About?

We're talking about the glass joint when we say 14mm vs 18mm bong - the opening where your bowl piece, downstem, or ash catcher connects to the bong. The number refers to the diameter of that opening, measured in millimeters. 

Let’s start with what it doesn’t affect - filtration, smoke density, or how high you get. What it does determine is which bong bowls and accessories are actually compatible with your piece.

That’s the entire reason this question matters. Drop a 14mm bowl into an 18mm joint and it'll wobble around or fall straight through. Try jamming an 18mm bowl into a 14mm joint and it won't even get close. 

What is a 14mm Bong?

A 14mm bong’s joint opening measures around 14.5mm in diameter. The industry rounds down to 14mm. This is the most common joint size on the market. There's a solid chance your small to mid-sized bong is 14mm. You'll also find this size on most bubblers and a good number of dab rigs.

Because 14mm is so widely used, the accessory selection is massive. Finding replacement bowls, downstems, and add-ons is never a problem. Browse our 14mm bowl collection or check out our 14mm ash catchers to see what's available for your piece.

What is an 18mm Bong?

An 18mm bong obviously has a wider joint opening, roughly 18.8mm in diameter. You'll typically see this size on large bongs, especially thicker, heavier pieces. The wider joint holds a bigger bowl, so you can pack more herb per load - perfect for shared sessions.

The accessory selection isn't quite as broad as 14mm simply because fewer bongs use this size, but there's still plenty to choose from here at Badass Glass. Check out our 18mm bowl options or our 18mm ash catchers if your piece takes the larger joint.

What About 10mm Bongs?

We know you came here to learn about the 14mm vs 18mm bong differences, but there's a third standard size worth knowing: 10mm. These are the smallest joints you'll run into, mostly found on mini bongs and mini dab rigs. You won't see 10mm joints on full-sized bongs. They're too narrow for the airflow most flower smokers want. 

The accessory market for 10mm is also way smaller than 14mm or 18mm. If you're weighing a smaller rig against a full water pipe, our bubbler vs bong comparison covers how the two styles differ beyond joint size alone.

Distinguishing Between Male and Female Joints

Joint size is one-half of the compatibility equation. The other half is gender. Yes, it sounds strange at first, but bong joints come in male and female configurations. It makes sense when you think about how accessories actually attach to the piece: 

• Female joint: The opening is recessed. Your bowl or downstem slides into it. This is the standard on most modern bongs.
• Male joint: The joint protrudes outward like a stem. Accessories slide over it. More common on older pieces and some dab rigs.

You need both the correct size AND the correct gender when shopping for accessories. A 14mm female bong takes a 14mm male bowl. Mix up either one, and nothing fits. That’s why you have to understand how to tell if your bong is 14mm or 18mm.

How to Tell if Your Bong is 14mm or 18mm

No ruler? No problem. Here's the fastest way to figure out how to tell if your bong is 14mm or 18mm - grab a US dime. Remove the bowl from your bong and hold the dime over the open joint. 

Does the dime drop inside the opening? You've got an 18mm joint. But if it sits on top without falling through, it's 14mm. A dime measures about 17.9mm across, which slots it right between the two sizes and makes it a perfect gauge. 

You're likely looking at a 10mm piece if the joint is noticeably smaller than the dime in both directions.

You can also check the original product listing. Most retailers include joint size in the specs just like they do bong thickness. When in doubt, remember that you can reach out to the experts at Badass Glass regarding any questions about compatibility for our accessories or bongs. 

Bringing Our 14mm vs 18mm Bong Comparison to a Close

The 14mm vs 18mm bong comparison really comes down to one practical question: what fits your piece? Neither size produces a better high, a smoother hit, or thicker smoke. The joint is a connector that determines which bowls, downstems, and ash catchers work with your bong, and that's about it.

Shopping for the right accessories gets simple once you know how to tell if your bong is 14mm or 18mm. Know your size, match the gender, and you'll never end up with a part that doesn't fit. Haven't checked yours yet? The dime trick takes three seconds. 

And when you're ready to shop, everything we carry ships same day on orders placed before 4 PM EST (free standard shipping included). Everything we sell has been handpicked from the best brands across the industry, so you can trust you’re getting the quality you deserve. Shop now!

Frequently asked questions

What's bigger, 14mm or 18mm?

18mm. The number is the diameter of the glass joint opening in millimeters, so an 18mm joint is about 4mm wider than a 14mm. Another option for how to tell if your bong is 14mm or 18mm if using your hand - 18mm is roughly thumb-width, 14mm is usually pinky-width (this isn’t a perfect science, obviously, since everyone has different hand/finger sizes)

Is 14mm the regular size for bong bowls?

It's the most common. The majority of small to mid-sized bongs use 14mm joints, which makes 14mm the default for replacement bowls and accessories. If you're ever guessing, 14mm gives you the best odds - but the dime test takes out the guesswork entirely.

Does the size of the bong affect the high?

The overall size of the bong can affect the experience since a larger chamber holds more smoke (translating to potentially bigger hits). But joint size specifically doesn't change the high. What actually makes a noticeable difference is filtration. Our percolator bong vs regular comparison explains how percolation matters more than joint diameter ever will.

Why does joint size matter, then?

Accessory compatibility - that's it. You need to match the joint size exactly when you need a new bowl, a replacement downstem, or want to add an ash catcher. A 14mm accessory won't fit an 18mm bong and vice versa. Knowing how to tell if your bong is 14mm or 18mm keeps you from wasting money on parts that won't work with your piece. When in doubt, reach out!