How Much Beer Is Left in a Keg

Last updated: 29 June 2026

Most pub licensees guess how much beer is left in a keg and lose money because of it. I did the same thing for years until I realised that a single partial keg going unaccounted for every week costs you real margin, week after week. Knowing how much beer is left in a keg sounds simple, but most operators still don’t do it properly — and that’s why stock variance stays hidden until it becomes a real problem. In this guide, I’ll show you the three methods that actually work, why the measurement matters more than you think, and how to build a count routine that catches losses before they become margin theft.

Why Measuring Keg Volume Matters

The number that actually matters is wet GP by line, not a single headline stock figure. Most pub managers run a monthly stocktake, notice a variance, and shrug. They do not know which kegs are the problem. They do not know if it is over-pouring, waste, cold temperature loss, or something else. Because they do not measure keg volume weekly, they cannot spot patterns.

I spent five years running stock on a tangle of spreadsheets and still losing track of partial kegs and spirit measures. The weekly variance ranged from 3% loss one week to a mysterious 2% gain the next — because I was not actually measuring anything, just guessing. Once I built a simple count routine around a dipstick and a set of scales, the weekly variance went from guesswork to a number I could trust within a fortnight. That number told me exactly where the problem was: poor line cleaning waste on one draught line, over-pouring on spirits, and a faulty temperature controller that was warming the cellar at night.

Without weekly measurement, you cannot see these problems. You only see the damage at month-end.

When you know how much beer is left in every keg, you can reconcile against till data the same day. This tells you whether the customer count matches the pour rate. If your till shows 80 pints of lager sold but your keg measurement says 95 pints came out, you have a line cleaning waste or over-pouring problem — and it is happening right now, not three weeks ago.

Method 1: The Dipstick Measurement

The dipstick method is the fastest and most reliable way to measure keg volume on draught lines. It works because a standard UK keg (typically a 50-litre) has a known internal diameter, and depth of liquid correlates directly to volume remaining.

What You Need

• A wooden dipstick (a marked ruler or baton, usually around 1 metre long)
• A calibrated dipstick chart specific to your keg size (supplied by most breweries)
• A notebook or mobile device to record readings

How to Do It

Open the top hatch of the keg (or use the dip tube if your keg has one). Lower the dipstick straight down until it touches the bottom of the keg. Mark where the liquid level sits on the stick, or read the pre-printed measurement. Compare this depth reading to your brewery’s dipstick chart for that keg size. The chart will tell you the volume remaining.

The entire measurement takes 45 seconds per keg. No calculations. No guesswork. You read the stick, cross-reference the chart, and record the number. Most pubs with 4–6 draught lines spend 10 minutes on a full cellar dip once a week.

The StockTap pub stock app allows you to log these readings in real-time from your phone, timestamp them, and automatically track variance week-on-week. This removes the spreadsheet step entirely.

Why This Works Better Than Estimates

Your eye is not accurate. A half-full keg looks the same at 20 litres and 28 litres depending on the angle of the light and whether the keg is sitting flat. The dipstick removes opinion. You get the same reading every time, and you can compare it to last week’s reading without debate.

Method 2: Weighing the Keg

The weight method works well for kegs that are harder to access or for tracking partial kegs that are not yet on the line. A full 50-litre keg of lager typically weighs around 70 kg (depending on beer type and keg condition). An empty keg weighs about 23–25 kg. The difference is the beer inside.

Equipment Needed

• A set of digital scales rated to at least 100 kg (commonly available for £40–80)
• A record of your empty keg weight (tare weight)
• A simple formula: (current weight – tare weight) ÷ weight per litre of beer

How to Calculate Volume from Weight

Beer weighs approximately 1.02 kg per litre (very close to water). So if a keg weighs 60 kg and your empty keg (tare) weighs 24 kg, then the beer inside weighs 36 kg. Divide 36 by 1.02, and you have roughly 35 litres remaining.

This method is slower than the dipstick (because you have to move the keg onto scales) but it is more portable. I use it for partial kegs stored away from the main line — the ones that are easy to forget and end up written off as waste at the end of the week.

When to Use Weight Instead of Dipstick

If your cellar is cramped and kegs are stacked, or if you receive partial kegs from the brewery, weight is faster than moving everything around to dip it. It is also useful for spotting kegs that are leaking slowly — if a keg loses 2 kg in a week with no line attached, you have found your problem.

Method 3: Pour-Out and Calculate

This method is simple but labour-intensive: disconnect the keg from the line, pour what is left into a measuring vessel, and record the volume. You then know the exact amount that came out of the line during that period.

Use this method only for the last keg on a line — the one you are about to remove anyway. Pour it into a bucket with volume marks, or use a measuring jug if the volume is small. This gives you an exact number with no chart or calculation needed.

The advantage is simplicity; the disadvantage is time and the risk of spillage. I use this method once a month as a sanity check against my dipstick readings. If my dipstick said 12 litres remained and the pour-out showed 11.5, my measurement is accurate. If it showed 8 litres, something is wrong with my technique or my chart.

Common Mistakes That Hide Stock Loss

Most pub stock ‘theft’ is actually measurement error and forgotten wastage. Here is where the real losses hide.

Poor Line Cleaning Waste

A draught line that is not cleaned properly can waste 2–3 pints per day in foam overflow. Nobody records it because it happens behind the bar. Over a week, that is 14–21 pints of unaccounted loss on a single line. If you run three draught lines and none of them are cleaned properly, you are writing off 40–60 pints a week and calling it variance.

Temperature-Driven Loss

If your cellar temperature drifts above 14°C, beer begins to absorb CO₂ from the line. The keg depressurises, and you lose volume without pouring a single pint. A warm cellar for one week can account for 1–2% keg loss on its own.

Over-Pouring (Especially Spirits)

Spirits hide losses in over-pouring because most pubs free-pour or use inaccurate measures. A 25ml free-poured measure is often 32–35ml. Multiply that across 200 spirit pours a week, and you have lost 1.5–2 bottles of spirits without anyone noticing. Weigh open spirit bottles on a set of scales at the start and end of each week. A bottle of vodka weighs roughly 1 kg. If it loses 150g in a week and your till shows only 120ml sold, you have a 30ml over-pour problem — and you can fix it with a proper measure or a pour spout.

Forgotten Wastage

A keg goes slightly flat and gets discarded. A spillage happens during a line change and no one writes it down. A guest complains about a pint and you remake it without recording the waste. These forgotten events add up to 1–2% loss a week at most pubs. Record all of them in a waste log next to your count sheet.

Building Your Weekly Count Routine

A proper weekly count takes 15–20 minutes for a six-line pub and requires no special skill — just discipline. Here is how to build it into your rota.

Pick a Fixed Day and Time

Monday morning before service is ideal — you can reconcile against the previous week’s till data while the pub is quiet. Pick the same time every week. If you skip a week, you lose the comparative data that reveals trends.

Measure All Draught Kegs and Partial Kegs

Use the dipstick on every keg on the line. Weigh any kegs in storage. Record the date, product, measurement, and any visible defects (leaks, flat beer, temperature issues).

Reconcile Against Till Data

Pull your till report for the same period (usually Friday close to Sunday close). Compare till pints sold against your keg measurement. If your till shows 180 pints of Guinness sold but your keg measurement says 195 pints came out, you have a 15-pint discrepancy. This is your waste, over-pour, or line loss for that period. Record it. If the same line is 15 pints out every week, you have a systemic problem on that line — poor cleaning, faulty regulator, or consistent over-pouring.

Record Everything in One Place

A spreadsheet works, but SmartPubTools builds a system designed specifically for this job. The StockTap pub stock app stores all your readings, calculates variance automatically, flags lines that are drifting out of tolerance, and shows you GP by line — which is the metric that actually matters to your profit.

After two weeks of consistent measurement, you will see patterns. After four weeks, you will know exactly which products are losing money and why. Most pubs that move from a messy spreadsheet to a disciplined count claw back 1–2 GP points within a couple of months.