Measuring liquor bottles for inventory comes down to three main methods: visually estimating how full each bottle is (called “tenthing”), weighing bottles on a scale, or using app-based tools that combine scales with software. The method you choose depends on how many bottles you’re counting, how precise you need to be, and what you’re willing to spend on equipment.
The Tenthing Method
Tenthing is the most common way bars measure open liquor bottles. You pick up each bottle (or eyeball it on the shelf), estimate how full it is to the nearest tenth, and record that number. A bottle that looks half full gets recorded as 0.5. One that’s about three-quarters full is 0.7 or 0.8. A nearly empty bottle might be 0.1.
The appeal is simplicity. You don’t need any equipment beyond a clipboard or spreadsheet. But tenthing has real accuracy problems. Two different people looking at the same bottle will often record different numbers, especially in the middle range where bottles are harder to read. A tenth of a standard 750ml bottle is 75ml, or about 2.5 ounces. That means your best-case margin of error on any single bottle is roughly two to three pours. For high-volume products like vodka or whiskey, that imprecision gets absorbed across many bottles. For expensive, low-volume products like premium scotch that might sell only one or two servings a week, a tenth of a bottle is far more than what was actually poured, making it nearly impossible to spot shrinkage.
If you use tenthing, consistency helps. Always have the same person do inventory. Hold bottles at eye level rather than guessing from across the bar. And count at the same time of day each period so you’re comparing like with like.
Weighing Bottles on a Scale
Weighing gives you a more precise count than visual estimation. The basic idea: if you know how much an empty bottle weighs and how much a full bottle weighs, you can put a partially full bottle on a scale and calculate exactly how much liquid is left.
To set this up, you need two numbers for each product you carry. The first is the tare weight, which is just the weight of the empty glass bottle with its cap or pour spout. The second is the full weight, the bottle when it’s sealed and unopened. Weigh one empty and one full container of each product and record both figures in grams, ounces, or pounds.
When you’re doing inventory, place each open bottle on the scale and record the reading. Subtract the tare weight from the current weight to get the weight of the remaining liquid. Divide that by the total liquid weight (full weight minus tare weight) to get the percentage remaining. For example, if an empty bottle of gin weighs 400 grams, a full bottle weighs 1,150 grams, and your open bottle reads 700 grams, you have 300 grams of liquid out of a possible 750 grams, or 40% of the bottle.
A decent digital kitchen scale works fine for this, though a scale that reads in grams gives you better precision than one that reads only in ounces. The upfront work is building your tare weight list. Once you’ve weighed one empty bottle of each brand, you can reuse that number every time since glass bottles of the same product weigh the same. Keep the list somewhere accessible so anyone doing inventory can reference it.
App and Bluetooth Scale Systems
Inventory apps speed up the process by combining a Bluetooth-connected scale with software that already knows tare weights for thousands of products. You scan a bottle’s barcode with your phone, set it on the scale, and the app calculates how much is left and logs it automatically. No clipboard, no manual math, no data transfer errors.
Several platforms offer this type of integration. WISK, Bar Patrol, and TavernTrak all support Bluetooth scales paired with mobile apps. BirchStreet lets you count using barcode scanners, smartphones, or tablets. Most of these apps maintain databases of bottle information, so you don’t need to manually record tare weights for every product. Many also connect to your point-of-sale system, which lets you compare what was poured against what was sold.
The tradeoff is cost. These platforms charge monthly subscription fees, and you’ll need to buy a compatible Bluetooth scale. For a bar with hundreds of open bottles across multiple stations, the time savings and accuracy improvement often justify the expense. For a small operation doing weekly counts on 30 or 40 bottles, a basic digital scale and a spreadsheet may be all you need.
Counting Full Versus Open Bottles
Full, sealed bottles are simple. Count them and multiply by the unit cost. The measurement challenge is only with open bottles, so keep your process organized by separating the two. Count all sealed bottles of a product first, then measure the open ones and add them as a decimal. If you have three sealed bottles of bourbon and one open bottle that’s 60% full, your total count for that product is 3.6 bottles.
An alternative to tenthing or weighing is counting by pours. If a 750ml bottle holds 25 ounces and your standard pour is 1.5 ounces, that bottle yields about 16 pours. You can estimate how many pours remain instead of thinking in tenths. This gives you a finer unit of measurement than tenthing, though it’s still a visual estimate unless you’re weighing.
How Often to Count
Weekly inventory is the standard for most bars. Counting less often than monthly makes it difficult to trace problems or hold anyone accountable, because too much time passes between measurements. High-volume or high-theft-risk products like premium spirits benefit from even more frequent counts. Some bars count their top 20 products daily and do a full inventory weekly or biweekly.
Whatever frequency you choose, consistency matters more than the interval. Always count on the same day, at the same time (before opening is ideal), and in the same order. This eliminates variables that would make your period-to-period comparisons unreliable.
Turning Measurements Into Useful Numbers
Raw bottle counts only become actionable when you plug them into a usage calculation. The standard formula is straightforward: take your beginning inventory (what you had at the start of the period), add any purchases or deliveries received during the period, then subtract your ending inventory (what you have now). The result is your usage, or cost of goods sold.
Beginning Inventory + Purchases – Ending Inventory = Usage (Cost of Goods Sold)
To find your pour cost percentage, divide that usage number by your liquor sales for the same period. A healthy liquor pour cost typically falls between 10% and 20% of sales. If your pour cost runs higher than that, it could indicate over-pouring, unrecorded comps, theft, or simply inaccurate inventory counts. This is exactly why measurement precision matters. If your tenthing estimates are off by even a few tenths per bottle across dozens of products, your usage calculation can swing by hundreds of dollars, making it impossible to tell whether you have a real problem or just a measurement problem.
Whichever method you use, the goal is the same: get a number precise enough that you can trust the math downstream. Weighing beats tenthing on accuracy. Apps with integrated scales beat manual weighing on speed. Pick the method that fits your volume and budget, then do it consistently.