Draft Beer Line Length Calculator
Balance your draft system - beer line length for your pressure, line type and rise.
Balanced 3/16" vinyl line, direct-draw kegerator (no rise)
| Serving pressure | Line length | Metric |
|---|
Computed with the same method the Brewers Association uses for its own direct-draw table (table 3.3, “Direct-Draw Draught System Balance at 38°F”), but at round pressures rather than the manual’s carbonation-linked ones. Where they overlap we match the manual to the inch on five of its seven columns. Add your own rise in the calculator above if your tower lifts the beer.
How it works
A draft system is balanced when the pressure pushing the beer is exactly cancelled by the resistance opposing it. Get that right and the beer arrives at the faucet at about atmospheric pressure, still carbonated, and pours cleanly at roughly 2 fl oz per second - about eight seconds to fill a pint. Get it wrong in one direction and you pour foam; wrong in the other and the pour crawls.
Resistance comes in two parts. Static resistance is gravity: lifting beer to a tap above the keg costs about half a pound per vertical foot, and a tap below the keg gives that pressure back (so it needs a longer line, not a shorter one). Dynamic resistance is the beer line itself, measured in pounds per foot of tubing. Whatever the height does not absorb, the line has to.
static resistance (lb) = rise (ft) × 0.5
required line resistance (lb) = serving pressure (psi) − static resistance
line length (ft) = required line resistance ÷ resistance per foot
Tubing resistance values
Every value in the selector is reproduced from one published table - table 4.1 of the Brewers Association Draught Beer Quality Manual, fourth edition. We ship the manual's eleven rows and nothing else: where a size and material is not in that table, it is not in this calculator.
| Type | Size | Resistance (lb/ft) | ≈ kPa/m |
|---|---|---|---|
| Vinyl / flexible | 3/16" ID | 3.00 | 67.9 |
| Vinyl / flexible | 1/4" ID | 0.85 | 19.2 |
| Vinyl / flexible | 5/16" ID | 0.40 | 9.0 |
| Vinyl / flexible | 3/8" ID | 0.20 | 4.5 |
| Vinyl / flexible | 1/2" ID | 0.025 | 0.6 |
| Barrier | 1/4" ID | 0.30 | 6.8 |
| Barrier | 5/16" ID | 0.10 | 2.3 |
| Barrier | 3/8" ID | 0.06 | 1.4 |
| Stainless | 1/4" OD | 1.20 | 27.1 |
| Stainless | 5/16" OD | 0.30 | 6.8 |
| Stainless | 3/8" OD | 0.12 | 2.7 |
kPa/m figures are our own conversion of the published lb/ft values (1 lb/ft ≈ 22.6 kPa/m), shown for metric users - the manual publishes the imperial column only.
What we deliberately do not do
We do not subtract a "1 psi faucet allowance". It is common in homebrew calculators, but neither the Draught Beer Quality Manual nor the American Homebrewers Association uses one, and we would rather match the published sources than carry an unsourced constant. We also do not model tower resistance, flow-control faucets, elbows or fittings - the manual notes a tower alone can range from zero to 8 lb, and only its manufacturer knows which. If you have a specified figure, add it to your pressure and re-run.
Sources: the balancing model, the 0.5 lb/ft convention and every tubing resistance value come from the Brewers Association Draught Beer Quality Manual, 4th edition (2019) - table 4.1 (p. 39) for resistances, p. 38 for the 0.43 lb/ft hydrostatic figure and the 0.5 lb/ft trade convention, table 3.3 (p. 28) for direct-draw lengths, and the worked examples on pp. 41-42 for the balance equation. The manual is published free by the Brewers Association. The same method and table are reproduced by the American Homebrewers Association in “A Balancing Act”, whose worked example our calculator follows step for step: 12.4 psi less 1 psi of gravity over 2 ft leaves 11.4 psi, and “11.4 psi ÷ 0.85 psi/ft = 13 feet of beverage line or so”. We show the unrounded 13.4 ft; the AHA rounds it to 13.
A balancing estimate, and a starting point rather than a final answer. The manual itself footnotes its table “provided as an example only - please consult your equipment manufacturer for exact values”, and real resistance varies with tubing brand, beer temperature, fittings and tower. Cut the line slightly long, then trim an inch or two at a time until a pint fills in about eight seconds.
Frequently asked questions
- Why does my draft beer pour all foam?
- An unbalanced line is one of the usual suspects. A balanced system dissipates the whole applied pressure across the line, so the beer reaches the faucet at roughly atmospheric pressure and stays in solution; too little line and the beer arrives still under pressure, breaks out as CO₂ through the tap, and you get a glass of foam. Lengthening the line is the fix for that - not turning the gas down, which just leaves you with flat beer that still foams. But line length is not the first thing to check. The Draught Beer Quality Manual's troubleshooting table lists temperature too warm at the faucet ahead of line length, then kinked line, applied pressure too high or too low, a defective coupler washer, a dirty system and a torn keg-valve seal. Confirm the beer is properly cold first, then balance the line.
- What is the beer line length formula?
- Two steps. First the resistance your line has to supply: required resistance (lb) = applied pressure (psi) − static resistance, where static resistance = rise (ft) × 0.5 lb/ft. Then line length (ft) = required resistance ÷ the tubing's resistance per foot. That is the Brewers Association Draught Beer Quality Manual method, worked exactly as the manual does it on pages 41-42. Note there is no extra "minus 1 psi" in it - see the FAQ below.
- How do I calculate beer line length by hand?
- Take your serving pressure - say 12 psi. Measure the rise from the middle of the keg to the faucet - say 4 ft - and multiply by 0.5 to get the static resistance: 2 lb. Subtract: 12 − 2 = 10 lb of resistance the line must provide. Divide by the resistance of your tubing: 3/16" vinyl is 3.0 lb/ft, so 10 ÷ 3.0 = 3.3 ft. That is the whole calculation; the tool above just does the arithmetic and the unit conversions for you.
- Does the height of the tap above the keg matter?
- Yes, and the sign matters too. Every foot the faucet sits above the middle of the keg costs about 0.5 lb of pressure to lift the beer, so you need less line. Every foot the faucet sits below the keg (a cooler above the bar, a tap lower than the keg) adds pressure, so you need more line. Enter a negative rise, or switch the direction selector to "drop", to account for it.
- Why 0.5 psi per foot and not 0.43?
- The true hydrostatic figure for beer is about 0.43 lb per vertical foot, and the Draught Beer Quality Manual says so explicitly. It then adds that "a figure of 0.5 lb./ft. is often used in the trade for ease of calculation, a convention that we will follow in this manual for purposes of discussion and example". We follow the manual's convention. On a home kegerator the difference is tiny - on a 4 ft rise it is 0.28 lb, about an inch of 3/16" line.
- Should I subtract 1 psi for the faucet?
- Some homebrew calculators do. We do not, because neither canonical source does. The Draught Beer Quality Manual balances applied pressure against static plus dynamic resistance with no faucet term, and notes that "items like couplers and faucets usually impart negligible resistance". The AHA's worked example likewise goes straight from 11.4 psi to 13 ft of 1/4" line with nothing subtracted. If your own faucet or tower has a manufacturer-specified resistance, add it as extra rise-equivalent pressure and re-run. A tower can be worth up to 8 lb.
- What line diameter should I use for a kegerator?
- 3/16" ID vinyl is the workhorse for home kegerators. At 3.0 lb/ft it is the highest-resistance tubing in the manual's table, so a typical serving pressure balances in only 3-5 ft - a length that actually fits inside the cabinet. Wider 1/4" vinyl (0.85 lb/ft) needs roughly 3.5× the run for the same job, and 5/16" (0.40 lb/ft) more than 7×, which is why those sizes belong on long draws and trunk lines rather than in a kegerator.
- Does this work in metric - for Australia, the UK or Europe?
- Yes. Switch the pressure unit to kPa or bar and the height unit to metres, and the result is given in metres as well as feet. The underlying resistance values are published in lb per foot; we convert them for display (3/16" vinyl ≈ 4.76 mm ID ≈ 67.9 kPa/m) rather than substituting a different table, so the metric answer is the same physics as the imperial one, not an approximation of it.
- Is there a beer line length table I can just read off?
- There is one on this page - the reference table below the calculator gives the balanced 3/16" vinyl length for common serving pressures at zero rise, which is the direct-draw kegerator case. The Draught Beer Quality Manual publishes a table for the same situation (table 3.3, "Direct-Draw Draught System Balance at 38°F"), though at the specific pressures that hold 2.3-2.9 volumes of CO₂ at 38°F rather than at round numbers. Where the two overlap, ours agrees with the manual to the inch on five of its seven columns; the manual's two end columns (9.2 and 15.6 psi) are printed a few inches longer than the arithmetic gives, and we have not tuned our model to match those two outliers.
- My pour is still wrong after fitting the calculated line. What now?
- Trim, do not rebuild. These resistance values are, in the manual's own words, "provided as an example only" - real tubing varies by manufacturer, and towers, couplers and flow-control faucets all add resistance the model does not know about. Start slightly long, then shorten an inch or two at a time until the pour takes about 8 seconds to fill a pint - the manual's target flow rate is 2 fl oz per second. If the beer is foaming and the line is already long, check the keg temperature before you touch the line: warm beer foams no matter how well balanced the system is.