How to check beer left in a keg without weighing

Last updated: 29 June 2026

Most pub licensees assume they need scales to know how much beer is left in a keg—and most of them are wrong. I spent years lugging scales around my cellar before realising that a working pub needs speed and reliability, not laboratory precision. The truth is, five simple techniques will tell you whether a keg is nearly full, half-empty, or running on fumes—and that’s all you actually need for a proper weekly stock count.

The reason this matters isn’t academic. A 1% stock loss on wet sales quietly costs a typical pub £3,000–£5,000 a year, and most of it happens because licensees don’t know what’s actually in their kegs. You can’t manage what you don’t measure. This article walks you through five practical ways to check how much beer is left in a keg without weighing, plus explains why accuracy in your cellar translates directly to profit.

The Tap Pressure Method

Tap pressure is the fastest way to estimate keg content and takes under ten seconds per barrel. A full keg of cask ale sits at around 2 bar of pressure; as it empties, the pressure drops. You won’t get an exact volume, but you can immediately tell if a keg is full, three-quarters full, half-full, or nearly done.

Here’s how it works: Feel the pressure regulator on top of the keg, or look at the gauge if your system has one. A full keg resists when you press the valve; an empty one gives immediately. After a few weeks, you’ll develop a feel for the subtle difference between a keg with 20% left and one with 50% left.

The limitation is that this method only works for cask ales and craft beers that sit under CO₂ pressure. Keg lagers and pressurised systems (which most commercial breweries use) will all sit at the same gauge pressure regardless of volume, so the pressure test won’t help you there. For those kegs, move to one of the other methods.

I use this as a quick daily check—a five-second feel of the pressure valve tells me whether to flag a keg for a detailed count later in the week. It’s not precise, but precision isn’t always the goal. Speed and consistency are.

The Acoustic Test

Tapping the side of a keg and listening to the resonance reveals liquid level with surprising accuracy, and most pub staff learn it in one shift. A full keg makes a dull thud; a half-full keg sounds slightly more hollow; an nearly-empty keg rings like a bell. The pitch and sustain of the sound change as the air space inside the barrel grows.

Method: Tap the keg about a third of the way up from the base, using your knuckles or a wooden stick. Listen to the tone. After you’ve done this a handful of times alongside known volumes (when you tap a full keg and a half-full one back-to-back), your ear calibrates. Within a couple of weeks, any competent bar staff member will be able to estimate keg volume to within 10–15%.

Why it works: Sound travels differently through liquid than through air. As the liquid level drops, more of the keg’s interior is air, so the resonance lengthens and the pitch rises slightly. It’s the same principle that lets you tell a nearly-empty glass of beer from a full one just by the sound.

The acoustic test is my second choice after the pressure method, because it requires zero equipment and works on all keg types. The only drawback is that in a noisy cellar or during a busy service, you might not hear the difference clearly—so always do this during a quiet moment and in the same place in your cellar each time.

The Visual Line Marker

Mark your cellar wall with a permanent marker or tape at the height of a full standard keg. Then mark lines at 75%, 50%, and 25% full. As kegs sit in your cellar, you can sight-check them against these reference lines without lifting or tapping anything.

To set this up correctly: Place a full keg in your normal storage spot. Mark the wall at the top of the keg. Then, empty it completely (or use a known-volume keg from your supplier), and mark the wall at 75%, 50%, and 25% as you pour out measured amounts. Take a photo of your reference marks so you can rebuild them if they fade.

This method works best if you rotate the same kegs into the same position in your cellar—which most pubs do anyway. The downside is that different keg brands have slightly different diameters, so your markers will be less accurate if you’re mixing Cask Marque, King & Barnes, and independent breweries in the same spot. But for a pub that uses mostly one or two suppliers, this is a legitimately quick visual check.

I use this in my own pub as a pre-count scan. Before I do my detailed weekly count, I walk the cellar and visually mark any keg that looks like it’s less than half full—that tells me which ones to dip or weigh more carefully.

The Dipstick Approach

If you want precision without scales, a dipstick is the right tool. A simple wooden or plastic rod marked with volume gradations lets you measure beer depth inside a keg and convert that to approximate volume.

How to make one: Cut a wooden stick or dowel to 600mm (long enough to touch the bottom of a standard UK 50-litre cask). Mark it with permanent pen at intervals—mark every 5cm, then use a simple proportional calculation to convert depth to volume. A standard cask is roughly cylindrical, so if the keg is 900mm tall, each 5cm of depth represents about 2.8 litres of beer.

Using the dipstick: Lower it gently to the bottom of the keg. Note the level where the beer surface meets the stick. Read the marking. Done. It takes 15 seconds and gives you a number you can record.

The advantage over scales is that a dipstick is cheap to make (under £5), always available, and doesn’t require the keg to be stationary or level. The disadvantage is that it only works if you can physically access the keg opening—so it won’t work on sealed or pressurised systems. Most cask ales and hand pumps work fine.

StockTap pub stock app has a built-in dipstick converter so you don’t have to do the math on your phone—just measure depth, enter the number, and it calculates volume for your cellar sheet automatically.

Combination Checks for Accuracy

The most reliable method isn’t any single technique—it’s using two or three together on the same keg. When I was running stock on a tangle of spreadsheets, I’d guess at volumes and lose track of partial kegs constantly. Once I built a simple routine around a dipstick and a set of scales, my weekly variance went from guesswork to a number I could trust within a fortnight.

Here’s the routine that works:

• Acoustic check first (five seconds)—quick estimate of whether the keg is full, half, or nearly empty.
• Dipstick second (15 seconds)—precise measurement of depth, converted to litres.
• Visual reference third (five seconds)—does the dipstick reading match your cellar marker? If not, you’ve spotted a measurement error before you record it.

If all three agree, you record the volume and move on. If they disagree, you re-measure. This catches mistakes and teaches your staff consistency fast. After a month, your team will be able to give you keg volumes accurate to within 5–10%.

The number that actually matters is wet GP by line, not a single headline stock figure. Spirits hide losses in over-pouring (a free-poured 25ml is often 32–35ml); draught hides it in poor cellar temperature and bad line cleaning waste; and most stock ‘theft’ is actually measurement error and forgotten wastage. Once your keg readings are consistent, you can reconcile them against your till data the same day and spot real leaks—not just counting errors.

Why Weekly Counting Beats Brewery Stocktakes

Many licensees assume the brewery’s stocktaker will catch any losses when they visit. That’s a comforting assumption and a costly one.

The brewery’s stocktaker comes quarterly (maybe monthly). In that gap, 1–2% of your wet sales can vanish: through over-pouring, line cleaning waste, cellar temperature swings that affect keg pressure, forgotten spillages, and genuine theft. By the time the brewery arrives, that loss has already become profit you can’t recover.

A weekly count using any of these methods catches that leak in real time. You spot a keg that’s dropping faster than it should, you investigate the line, you find the blockage or the temperature fault, you fix it before the next week’s damage. That disciplined routine is why pubs that move from a messy spreadsheet to a weekly count claw back 1–2 GP points within a couple of months.

The brewery stocktake is a compliance check. Your weekly count is a profit check. You need both, but the weekly count is the one that actually saves you money.

For more information, visit SmartPubTools.