How many pints in a firkin saleable

Last updated: 29 June 2026

Most pub licensees can tell you the price of a pint, but ask them to name the exact cask sizes in their cellar and you’ll get a lot of blank stares. A firkin holds 40.9 litres, which equals 72 pints of beer — and if you’re not tracking this figure accurately during your weekly stock count, you’re almost certainly bleeding money without knowing it. After 15 years running a Marston’s pub, I can tell you that the difference between knowing your numbers and guessing them is anywhere from £3,000 to £5,000 a year in silent losses. This article explains what a firkin is, why the pint count matters for your stocktake, and how to build a count routine that actually catches shrinkage before it costs you.

What Is a Firkin and How Many Pints Does It Hold?

A firkin is a quarter-barrel cask holding exactly 40.9 litres, or 72 pints of draught beer. This is the standard size you’ll see in most UK pubs. If you’re working in draught lager, cider, or ale, the firkin is your baseline unit of measurement.

There’s also a pin (9 pints) and a kilderkin (half-barrel, 144 pints), but the firkin is what you’ll count most often. Knowing this figure by heart isn’t pedantic — it’s the foundation of accurate stock reconciliation. When you dip a cask or weigh an open keg, you’re converting a physical measurement into pints, and pints convert into till data. If you get the cask size wrong, your entire count is wrong.

In practice, most of your cellar stock will be made up of full and partial firkins. A full firkin should tie out to your purchase invoice, and every partial firkin should be logged by depth or weight the same day you open it. The number matters because it becomes the numerator in your weekly variance calculation: actual stock on hand divided by what you sold equals your shrinkage percentage.

Why This Matters for Your Weekly Stock Count

Here’s the thing most pub accountants won’t tell you: your EPOS doesn’t know if you’ve poured a free pint, if your line cleaning has wasted a gallon of good beer, or if a cask was sat in a warm cellar and went off. Your till tells you what sold. It doesn’t tell you whether you made money on it.

That gap — between what you sold and what you actually had to give away to sell it — is where most licensees lose 0.5% to 2% of wet sales revenue. For a typical pub turning over £8,000 a week in draught beer, 1% loss is £80 per week, or roughly £4,000 a year. Most pubs that move from a messy spreadsheet to a disciplined weekly count claw back 1–2 gross profit points within a couple of months.

The specific number of pints in each cask size matters because it sets the standard against which you measure variance. If a firkin is 72 pints and you log it as 70, you’re creating a 3% built-in error. Multiply that across five firkins and you’ve lost track of 10 pints of sellable beer. Over a month, that’s 40 pints of unaccounted-for loss. That’s not a spreadsheet problem — that’s money walking out the cellar door.

This is where disciplined measurement comes in. When I overhauled my own stock routine, I moved from visual guessing to two tools: a dipstick for casks and a set of scales for open spirit bottles. The weekly variance went from a completely opaque figure I couldn’t trust to a number I could reconcile against till data the same day. Within a fortnight, I knew exactly where the loss was happening: poor line cleaning was wasting 2–3 pints a week, and I was over-pouring spirits by about 30%.

Using StockTap pub stock app to log these measurements daily means you’re not relying on memory or a crumpled notebook. You’ve got a timestamped record of every cask depth, every partial keg weight, and every tapped line. When the variance shows up, you can actually trace it back to a specific line or date instead of shrugging and writing it off.

How to Record Partial Kegs and Avoid Measurement Error

The moment you tap a firkin, you start a countdown clock. You need to know, on the day you open it, exactly how many pints are in there. Then every time you count, you measure how much is left and log it. This is non-negotiable if you want accurate stock.

There are three ways to measure a partial cask:

• Dipstick: A marked pole that shows you the liquid depth. You read the depth, convert it to litres using the cask’s calibration table, and translate that to pints. A firkin dipstick usually shows you the pint level directly.
• Scales: Weighs the cask with beer in it. A full firkin weighs about 50 kg. Every litre of beer weighs roughly 1 kg. Subtract the tare weight of the empty cask and you’ve got your contents in litres.
• Visual estimation: Don’t. This is where 90% of cellar errors come from.

I prefer the dipstick for casks and scales for open spirit bottles. A dipstick takes 10 seconds per cask. Scales take 20 seconds per open bottle. Every Friday morning I spend 15 minutes in the cellar with these two tools, log the numbers, and I have a stock position I can actually trust by lunchtime.

The key insight that separates diligent licensees from the rest is understanding that measurement error is not the same as loss. If you measure a cask as 35 pints when it’s actually 36, that’s a 3% error in your count, not a 3% loss in your cellar. Log it correctly and reconcile it the same day, and you’ve got visibility. Guess and wait until month-end, and you’ve got a £200 variance that you can’t explain or fix.

Common Mistakes When Counting Firkins and Casks

After running stock counts in my own pub and helping other licensees fix theirs, I’ve seen the same mistakes show up again and again:

• Confusing cask sizes during count: You write down “72 pints” for every draught line without checking if it’s actually a firkin, a kilderkin, or a partial keg. Check the label or the invoice every time.
• Forgetting to log wastage: You change a line, the old cask is 10 pints short, and you assume it’s loss. You didn’t log that you dumped 8 pints because the beer had gone off. That’s not loss — it’s cost of goods sold, and it needs to be recorded separately.
• Not measuring at the same time every week: Monday’s count and Friday’s count are measuring the same stock at different points in the week. You need a fixed count day to keep weekly variance meaningful.
• Relying on the brewery stocktaker: The brewery’s rep comes quarterly and does a full count. By then you’ve got three months of unreconciled variance. You won’t know if you lost it in month one or month three. Weekly counts are your responsibility, not theirs.
• Not reconciling till data the same day: You count the stock on Friday but don’t check what the till says was sold until the following Tuesday. By then you’ve forgotten which lines you adjusted or which casks you opened.

The most expensive mistake is assuming your spreadsheet is tracking accurately when it isn’t. I ran my cellar on spreadsheets for five years. I recorded every cask opening, every partial measurement, every line change. I still lost track of stuff because I wasn’t cross-referencing against till data, and because I wasn’t measuring the same way twice. A dipstick one week and a visual estimate the next gives you noise, not data.

Building a Reliable Cellar Count Routine

Here’s exactly what I do now, and what actually works:

• Pick a fixed count day: Every Friday at 11 a.m., before service. Same time, same day, every week. You’re counting after the previous night’s sales are rung through.
• Use a dipstick for every cask: Don’t estimate. Measure every single cask and log the depth. A firkin with a 15-inch dipstick reading is roughly 50 pints. Be consistent with your measurement point.
• Weigh every open spirit bottle: A 70cl bottle of spirits should weigh about 800g full. Weigh it and you know exactly how many 25ml measures are left. This is where most over-pouring hides.
• Log it in one place: Not a notebook, not three different spreadsheets. One app, one device, one single source of truth. SmartPubTools makes this non-negotiable because you need to be able to see your full cellar state and reconcile it against till data instantly.
• Reconcile the same day: Your till says 280 pints of lager sold. Your stock count says you had 200 pints on hand at the start of the week and 50 at the end. 200 minus 50 equals 150 pints that should have come out of stock. You’ve got a variance of 130 pints. Find it before the next week starts.

That last point is the one most people skip. They count the stock, log the numbers, and move on. A week later they think about reconciliation and by then it’s too late to trace the loss back to a specific line or date. The discipline that actually pays is the daily measurement plus the same-day reconciliation against till data. Do that and you’re clawing back 1–2 GP points within two months.

Building this routine takes three weeks to establish and costs almost nothing in equipment time. A dipstick is £15. A set of kitchen scales is £20. A notebook is free. The discipline is where most licensees fall down — not the tools. But if you use the right app to log your measurements, the discipline becomes automatic because you’re not trying to remember numbers or hunt down a spreadsheet file.