By Dan Smullen
Foamy pours and dead-slow pours almost always trace back to the same thing: a beer line that is the wrong length for your setup. This calculator takes your regulator pressure, the rise from keg to faucet, and your tubing size, and gives you the line length that balances the system.
Calculate your beer line length
How a balanced draft system works
Your CO2 regulator holds the keg at a set pressure to keep the beer carbonated. That same pressure pushes beer through the line to the faucet, and by the time it gets there, you want almost none of that pressure left, otherwise it comes out foamy. The beer line’s own friction is what soaks up the leftover pressure, so getting the length right is what makes a system ‘balanced’.
This calculator subtracts the small pressure loss from lifting beer up to the faucet, then divides what is left by how much resistance your chosen tubing creates per foot, to land on a length that uses up almost exactly the right amount of pressure.
Picking a tubing size
Standard 3/16″ ID vinyl is what most kegerators ship with, and it needs the shortest runs, often just a few feet. Wider tubing like 1/4″, 5/16″ or 3/8″ creates far less resistance per foot, so it needs a much longer run to balance the same pressure, which is why bars with long draw lines from a back cooler tend to use wider tubing.
If your calculated length comes out awkwardly short or long for your build, switching tubing size is usually the easier fix, rather than changing your carbonation pressure.
Frequently asked questions
Why does line length matter for a kegerator?
A "balanced" draft system uses the beer line's own resistance to soak up the leftover CO2 pressure after it overcomes the height the beer has to rise, so beer arrives at the faucet at close to atmospheric pressure. Too short a line and the pour comes out foamy; too long and it dribbles and takes forever to pour.
What pressure should I enter?
Use the regulator pressure your carbonation setup actually needs to hold your target CO2 volumes at your keg's serving temperature, the same figure the Carbonation Calculator or Keg Carbonation Calculator on this site gives you.
Why does tubing diameter change the answer so much?
Narrower tubing creates far more friction per foot, so it needs a much shorter run to absorb the same pressure. Standard 3/16" line needs roughly 3 psi of resistance per foot, while wider 3/8" bar line needs over ten times that length to absorb the same pressure, which is why long bar draw lines use wider tubing.
What counts as "rise" if my kegerator has a tower or a long horizontal run?
Rise is the vertical distance only, from the beer-out post on the keg coupler to the faucet. Horizontal runs add a small amount of extra friction too, but the standard home-kegerator method used here only accounts for vertical rise, which is the dominant factor in most single-tap setups.
More homebrewing calculators
This is one tool in the full homebrewing suite. Whatever stage of the brew you are at, there is a calculator for it.