Beer keg measurement chart explained

Last updated: 26 June 2026

Most pubs lose £3,000–£5,000 a year to stock loss on draught alone, and half of them don’t know it’s happening because they’ve never dipped a cask properly. A proper beer keg measurement chart isn’t just a nice-to-have — it’s the difference between knowing your stock position and guessing. If you’re running a pub without a systematic way to measure partial kegs, every line check is just theatre. This guide walks you through standard beer keg sizes, how to use a dipstick accurately, and why a weekly count routine catches the losses that brewery stocktakers miss.

Standard UK beer keg sizes and litres

There are five standard draught keg sizes used in UK pubs. Knowing the difference between them isn’t academic — if you’re dipping a firkin and reading from a barrel chart, your measurement is worthless.

The most effective way to measure beer stock is to know your keg size first, then use the correct measurement chart for that size, because each vessel has a different dipping depth and volume conversion.

• Pin — 11 litres (2.4 gallons). Rarely used now except for cask ales in smaller outlets. Full depth: approximately 45 cm.
• Firkin — 18 litres (4 gallons). Common for craft ales and some craft lagers. Full depth: approximately 50 cm.
• Kilderkin — 36 litres (8 gallons). The working horse for most keg lagers and mainstream draught. Full depth: approximately 70 cm.
• Barrel — 50 litres (11 gallons). Less common in UK pubs, more typical for export or high-volume venues.
• Hogshead — 57 litres (12.5 gallons). Rarely seen except in large hotel or function space cellars.

If you’re running more than one font of the same beer, check the keg tags. A brewery won’t always send the same size — you might get a kilderkin one week and a barrel the next, and if you don’t spot it, your dip reading is instantly unreliable.

How to dip a cask and read the measurement

Dipping a cask sounds simple and it is — until you do it wrong for the first time and realise you’ve been measuring from the wrong point. Here’s the proper method.

The dipping process

• Clean the top of the cask with a cloth. Dust and settled sediment skew the reading.
• Remove the shive (the wooden or plastic plug on top) slowly. Let pressure equalise — don’t force it.
• Lower the dipstick straight down until it touches the bottom of the cask. It must be vertical, not angled.
• Mark where the liquid surface meets the stick, or note the measurement if using a graduated dipstick.
• Withdraw the stick carefully and read the wet mark against the scale printed on it.
• Replace the shive hand-tight — not hammer-tight, you’ll damage it.

If you’re using a wooden dipstick, the wet mark shows as a slight darkening of the wood fibres. If you’re using a metal or plastic graduated stick, the measurement is printed directly on the scale.

One detail most pubs miss: always dip from the same position on the cask. If you dip from the tap end one week and the shive end the next, the reading will vary slightly because the cask isn’t perfectly level. Consistency matters more than perfection.

Partial keg volume chart for common sizes

A dip reading is useless without a conversion. Here are the most common sizes and their approximate volume at standard dipping depths.

Kilderkin (36L) — most common in UK pubs

• Full depth: 70 cm = 36 litres
• 70 cm (full) = 36 litres
• 60 cm = 30.8 litres
• 50 cm = 25.7 litres
• 40 cm = 20.5 litres
• 30 cm = 15.4 litres
• 20 cm = 10.3 litres
• 10 cm = 5.1 litres
• 5 cm = 2.5 litres or less (consider rotating)

Firkin (18L) — craft ales and smaller fonts

• Full depth: 50 cm = 18 litres
• 50 cm (full) = 18 litres
• 40 cm = 14.4 litres
• 30 cm = 10.8 litres
• 20 cm = 7.2 litres
• 10 cm = 3.6 litres
• 5 cm = 1.8 litres or less (consider rotating)

Barrel (50L)

• Full depth: 75 cm = 50 litres
• 75 cm (full) = 50 litres
• 60 cm = 40 litres
• 45 cm = 30 litres
• 30 cm = 20 litres
• 15 cm = 10 litres

These conversions are approximations based on standard cylindrical keg geometry. Exact volumes vary slightly by manufacturer, but the error is small enough that for weekly stocktaking purposes, these figures are reliable within 0.5–1 litre per reading.

If your brewery or distributor supplies a different chart, use theirs — but verify it matches the keg size tags on your stock. At my own pub, I built a simple laminated card with the three most common sizes printed on it and pinned it in the cellar. No guessing, no phone calls to the brewery. The card lives next to the scales.

Temperature, wastage and measurement accuracy

Here’s what brewery stocktakers and most pub managers don’t talk about: the keg measurement chart assumes the cask is at a consistent temperature. If your cellar swings between 10°C and 16°C, the volume of the beer itself changes slightly due to thermal expansion, and so does the accuracy of your reading.

Cellar temperature drift is one of the three hidden loss channels most pubs never measure, along with over-pouring on draught and line cleaning waste.

Your cellar temperature should sit between 12°C and 14°C for lager kegs, and 13°C–15°C for cask ales. If it’s swinging, you’re not just affecting the accuracy of your measurements — you’re also affecting the quality of the beer and accelerating the rate at which it oxidises, which shows up as a stock variance that looks like theft but is actually product degradation.

Line cleaning waste is the other silent killer. Most pubs clean their draught lines once a week. If you’re pulling 2–3 litres per line to flush them clean, that’s 10–15 litres a week gone before a single pint is poured. Most pubs don’t count it as wastage — they assume it’s part of the pour — but it’s not. It sits between the previous cask and the new beer in the lines. If you’re not logging it in your weekly count, your stock variance will be 5–10 litres positive every Monday morning, and you’ll never know why.

Over-pouring on draught is harder to catch, but it’s happening. A free-poured 20ml measure is often 24–28ml. A 25ml measure is regularly 32–35ml. Over the course of a week, that’s another 5–8 litres vanishing into the till rounding up, not theft.

Building a weekly line check into your stocktake

The brewery stocktaker counts what left the cellar. You need to count what’s left in it, because the difference between those two numbers is where your margin disappears. A proper weekly routine takes 20 minutes and catches all three loss channels at once.

Your weekly cellar count checklist

• Dip every active draught cask or keg — record the depth reading and convert to volume using your measurement chart.
• Weigh any open spirit bottles — spirits hide over-pouring more easily than draught because there’s no visible consumption in the cask. A scale spot-check on your top three spirit sellers catches 80% of the loss there.
• Note the cellar temperature — if it’s outside 12–14°C, log it and investigate why.
• Log line cleaning waste — if you cleaned lines that week, deduct the estimated volume (usually 2–3 litres per line) as a planned wastage entry.
• Reconcile against till data the same day — compare what the till says sold versus what the dip says left the cask. The variance tells you about over-pouring, theft, or measurement error.

At my own pub I was running stock on a tangle of spreadsheets and still losing track of partial kegs and spirit measures. I built a simple count routine around a dipstick and a set of scales, and the weekly variance went from guesswork to a number I could trust within a fortnight. Within two months, that routine had revealed I was losing nearly 8 litres a week on draught — not through theft, but through over-pouring during busy service and nobody logging line cleaning waste. Once I saw the number, fixing it was simple: a standard measure, a till prompt for wastage, and a weekly dip. My stock variance went from ±12 litres to ±1.5 litres. The margin recovery was just under 1 GP point in the first month.

Use StockTap pub stock app to log these readings. It automates the conversion from dipstick depth to volume, keeps a rolling record of your variance, and flags temperature drifts before they become a problem. But the system itself — the discipline of measuring the same thing the same way every week — is what matters. The tool just makes it frictionless.

Common measurement mistakes and how to avoid them

I’ve made most of these mistakes myself, and I’ve watched plenty of other licensees repeat them. Here’s what kills the accuracy of a beer keg measurement chart.

Reading the chart for the wrong keg size

This is the most common error. A 50cm dip on a firkin (18L) is about 50% full, so roughly 9 litres. A 50cm dip on a kilderkin (36L) is about 71% full, so roughly 25.7 litres. If you use the wrong chart, you’re out by 16 litres on a single cask. Check the keg size tag every time.

Dipping from different positions on the cask

Casks aren’t perfectly level. If you dip from above the tap one week and from above the shive the next, you’ll get slightly different readings even though the volume hasn’t changed. Pick one position and stick to it.

Not accounting for cask head space

A full cask isn’t actually full — there’s always a small air gap at the top to prevent pressure buildup. The standard charts assume you’re measuring to the liquid surface, not the top of the cask. If you’re measuring to the shive plug instead of the liquid level, your reading will be consistently low by 1–2 litres.

Ignoring cellar temperature variation

If your cellar temperature swings by 4–5 degrees during the week, your dip readings will vary slightly even though the physical amount of beer hasn’t changed. Log the temperature every time you dip. If it’s drifting, fix the root cause (faulty temperature controller, door left open) rather than spending time trying to reconcile measurements against a moving baseline.

Not dipping partial kegs before rotation

The most frustrating variance happens when you rotate a cask out when it still has 3–4 litres in it. You dip it on Tuesday at 4 litres, it sits until Friday, then you empty it into a container or use it to top up another cask without logging it again. The following week, that missing volume shows up as unexplained variance. Always dip immediately before you move a cask, and log it as a pour-off or top-up so the till can account for it.

Why accurate keg measurement matters to your bottom line

A 1% stock loss on wet sales quietly costs a typical pub £3,000–£5,000 a year. A proper weekly line check catches it. Most pubs that move from a messy spreadsheet to a disciplined count using a SmartPubTools approach claw back 1–2 GP points within a couple of months. That’s not because they’ve stopped theft — it’s because they’ve stopped leaking money through measurement error, wastage they forgot to log, and over-pouring they didn’t know was happening.

The number that actually matters isn’t a single headline stock figure — it’s wet GP by line. Spirits hide losses in over-pouring, draught hides it in poor cellar temperature and bad line cleaning waste, and most stock ‘theft’ is actually measurement error and forgotten wastage. Weigh open spirit bottles, dip every cask and partial keg, and reconcile against till data the same day. That discipline is worth thousands.