February 09, 2024

Figuring Alcohol: The Science of Pouring

Figuring Alcohol: The Science of Pouring

"Bartending is an art form that requires skill, precision, and creativity. But it’s not just a job; it’s a way of life. Bartenders have a long-standing tradition of following beliefs and superstitions passed down through generations....As bartending became more of an art form, superstitions evolved as well", according to BartenderTraining.

So, why is 'free pouring' so entwined in bartending mythology and superstitions? Is there Math or Science behind the bigger story to counter the heart felt passion of free pouring?

Whichever side of the debate you’re on... it’s fair to say that free pouring involves passion and heart, whereas jiggering (figuring) is more a discussion confined to the library of the mind.

So putting this aside, let’s look at some of the 'why' before we get into the math and science!

Free Pouring Passion

There’s something riveting watching a bartender doing their thing. Almost the equivalent of a martial arts “pouring carta” or “liquid tai chi”, connecting a mixologist and guest in a sublime moment of magic!

The free pouring magic comprises 3 distinct elements:

  • Mastery/Respect: Like a London cabbie passes the “Knowledge”, bartenders demonstrate mastery through bottles via liquids.
  • Dexterity: Conductors lead orchestras, so bartenders twirl the wrist, execute bottle cuts and bottle bounce to affirm their nuanced control over the “flow de vie”.
  • Ring Mastery: Step right up, watch the show, and see the bartender defy gravity. Be amazed of the control of flame, unbridled ice taming, impressive shaking. Delivering to you, the thirsty guest, a liquid exception in a glass!

When free pouring is considered within this context, it’s hard for science to compete.

The Science

So what’s the central tenant anchoring the free pouring thought process? The answer comes down to a simple number 3.

The magic of 3, or the 3 seconds taken to pour 1 shot (nip or serve) of alcohol via a traditional speed pourer. The science is a combination of gravity, airflow and liquid to create a form of mathematical absolutism... or so we’re led to believe!

Based on the 3 count system, let’s break time into discrete volume equivalents.

Time Volume
.5 second 5 mL or ⅙ Oz
1 second 10 mL or ⅓ Oz
2 seconds 20 mL or ⅔ Oz
3 seconds 30 mL or 1 Oz

Observation: As 3 is an odd number, not divisible by any other number other than itself or 1, we will see some rather weird fractional times to equate to discrete dispensing amounts.

To simplify things, most bartenders use the 4 second count where each count equals half an ounce poured. This still, however, varies with the bartender counting speed, degree of the bottle tilt and the actual pourer used.

Question: How do the above times relate to what constitutes a shot or serve of alcohol?

Answer: Doesn't that depend on one’s country or jurisdiction?

Legislative Pouring Volumes

There are also other accepted international serves, it’s quite staggering! See and compare the different geographic areas and their various standard pouring volumes with arising time equivalents, based on the 3 second count.

Country Standard Serve Pouring Time (Seconds)
Europe   20 mL  2
Europe   40 mL  4
United Kingdom   25 mL  2.5
United Kingdom   35 mL  3.5
United Kingdom   50 mL  5
USA / Canada   ½ Oz  1.5
USA / Canada   ¾ Oz  1.75
USA / Canada   1 Oz  3
USA / Canada   1¼ Oz  3.75
USA / Canada   1½ Oz  4.5
Australia / New Zealand / Asia   15 mL  1.5
Australia / New Zealand / Asia  30 mL  3

Now, let’s go deeper into the four components that can influence free pouring.

Tracking Time

Bartenders hone their 1, 2 and 3 second pouring via practice. Interestingly, there’s a correlation within the bartending community of free pouring accuracy and sexual prowess. At a guess, maybe it’s like liquid succumbing to mastery.

Some of the widely accredited techniques for maintaining free pouring accuracy:

  1. Counting according to internal syncopation and varies from person to person.
  2. Muscle memory and training repeatedly using a bartender pour test kit (BarCheck™) and where one feels the time to mentally imagine a pouring volume.

    This all makes sense, right... except, what happens to accuracy when a bartender is momentarily distracted or tired? Based on the figures above, doesn’t a blink of the eye, representing a part of 1 second, equate to pouring 5 mL or ⅙ Oz of alcohol? If this volume is then over-poured, could this become somewhat problematic, particularly when replicated by hundreds of drinks a night?


    Viscosity is the notion that volume flow rates change when a spirit or liquid is less runny than say the consistency of vodka due to:

    1. Sugar content
    2. Cream or milk content

    Viscosity is also affected by factors such as heat and cold... the warmer a liquid the runnier it is, the colder a liquid the slower it flows. Wouldn't this suggest that one’s free pouring calculations must change to accommodate for the differences of viscosity? Is there a formula or technique to precisely work this out? If there is, it’s probably safer to call it guessing!


    Timing works if the speed which liquid traverses through a speed pourer is uniform. What happens to liquid flow rates when a bottle is tilted, does the flow rate alter by the remaining volume of liquid and/or air left in a bottle? Do air pressure and gravity impact pour flow? What about temperature and altitude?

    Speed Pourers

    These are the tools inserted to a liquor bottle to pour from into any kind of receiving or serving vessel. Like every other multi-dimensional aspect to free pouring, they’re made in different factories with different manufacturing techniques, material and dimensions. Each variation changing the speed of liquid flow rates.

    Check out some of the examples below… pretty easy to see how the pour out points or mouths vary in diameter.

    Pour Spout Diameter Varies | Überbartools™

    Its all too confusing... better use a jigger and a better pourer.

    It’s unbelievable how many related and unrelated variables there are to dispensing alcohol consistently. There’s too much at stake to focus on trying to be consistently accurate by imagining the outcome desired.

    To save a whole lot of pain from over-pouring, second guessing, compliance issues... this could be the best time to invest in accurate and better tools such as the Perfect Pour System.

    Yes, using a jigger is really boring... however if the desired outcome is a guest reordering another drink, game over. Go figure with a jigger!