How to Bottle Homebrew Beer (and Carbonate It Without Bottle Bombs)

First, make sure it is actually done fermenting

Before you touch a single bottle, you need to know that fermentation has truly finished, because bottling early is the number one cause of bottle bombs. Active yeast, plus a sealed bottle, plus leftover sugar equals pressure with nowhere to go, and eventually a glass grenade in your closet.

The only reliable way to check is a hydrometer, not the airlock. A quiet airlock tells you very little, since a beer can look perfectly still and still have a few points left to go. Take a gravity reading, wait two or three days, then take another. If the number has not moved, fermentation is done and you are clear to bottle. For most standard ales that final gravity lands somewhere around 1.010 to 1.015, but the stable reading matters far more than the exact figure, because the right number depends entirely on your recipe.

This guide picks up at bottling day. If you are earlier in the process and want the whole arc from ingredients to first pour, our full homebrewing hobby guide covers the brew day itself. Everything below assumes you have a finished, flat beer sitting in the fermenter, ready to carbonate.

Prime it: the sugar dose that carbonates the beer

Bottled beer carbonates itself. You add a small, measured amount of fresh sugar, the surviving yeast eat it inside the sealed bottle, and the carbon dioxide they give off has nowhere to escape, so it dissolves into the beer as fizz. That is bottle conditioning, and the whole thing lives or dies on getting the sugar amount right.

For a standard 5 gallon batch, the default is about 3/4 cup of corn sugar (dextrose), which is roughly 4 to 4.5 ounces, or around 130 grams. That lands you near 2.4 volumes of carbon dioxide, which is normal pub fizz for something like a pale ale or an amber. Plain white table sugar works too, and you use a touch less of it, but corn sugar ferments cleaner and is what most kits include, so start there.

One detail quietly trips people up: how fizzy your beer ends up also depends on how warm it got after fermentation, because warmer beer holds less leftover carbon dioxide and needs a little more sugar to reach the same fizz. That is why online priming calculators ask for the beer's warmest recent temperature. If you want to be precise, or you are carbonating a fizzier style, plug your batch size, beer style, and temperature into any free priming calculator. If you just want it to work, 3/4 cup of corn sugar for 5 gallons of room-temperature ale is a safe, boring, reliable number.

To use it, boil the sugar in about two cups (16 ounces) of water for five minutes to make a clean syrup and kill anything living in it, then let it cool. And if measuring makes you nervous, carbonation drops are a genuinely good beginner shortcut: you drop one tablet into each 12 ounce bottle and skip the math entirely.

Fill, cap, and wait it out

Now the actual bottling. Sanitize everything that will touch the beer from here on: bottles, caps, siphon, bottling wand, and the bucket if you use one. Star San is the standard no-rinse sanitizer, mixed at 1 ounce per 5 gallons of water, with a minute or two of contact time. The foam is fine, do not rinse it off, just let it drain. Sanitation is nobody's favorite part, but a wild yeast or a stray bacteria getting in now is exactly how a good batch turns sour or starts gushing weeks later.

Add your cooled priming syrup to an empty, sanitized bottling bucket, then siphon the beer out of the fermenter on top of it. Two rules here. First, siphon gently and keep the tube tip below the surface, because splashing folds oxygen into finished beer and gives it a stale, wet-cardboard or sherry-like flavor a few weeks on. Second, leave the layer of settled yeast and sediment (the trub) at the very bottom of the fermenter behind. The transfer itself mixes the sugar in evenly, so there is no need to stir.

Fill each bottle with a bottling wand, which stops the flow the moment you lift it off the bottom and leaves the right gap for you. Aim for about an inch of headspace at the top, since the yeast needs that little pocket of air to work. Cap with sanitized caps and a capper, and make sure you are using proper pry-off bottles or flip-top, Grolsch-style bottles. Screw-top twist-offs will not seal reliably and tend to leak your carbonation away.

Then the genuinely hardest part: waiting. Stand the bottles upright somewhere around 70F (21C) and leave them two to three weeks. Much cooler than about 60F and the yeast go sluggish and the beer stays flat, so do not stash them in a cold garage. After a couple of weeks, chill one bottle for a day and open it over the sink the first time, just in case. If it hisses and pours with a bit of head, the rest of the batch is ready to drink.

Common mistakes (and how to spot them)

Nearly every bottling disaster is one of a small handful of errors. Knowing them ahead of time saves you a sticky closet and a case of flat beer.

• Bottling too early. If fermentation is not truly finished, the leftover sugar plus your priming sugar can over-pressurize the bottles into bottle bombs. Confirm a stable final gravity first, every single time.
• Overpriming. Eyeballing the sugar, or tossing in a little extra for good measure, is the other road to bombs and gushers. Weigh or measure it properly, and when in doubt aim slightly low.
• Splashing during the transfer. Oxygen is the enemy of finished beer. If your bottles taste like wet cardboard or cheap sherry after a few weeks, this is almost always the reason. Siphon slowly and keep the tube submerged.
• Skipping sanitation. A batch that slowly sours, or that gushes and over-carbonates over time, usually caught an infection at bottling. Sanitize everything, no shortcuts.
• Using the wrong bottles. Twist-off bottles and a loosely crimped cap will quietly bleed carbonation and leave you with flat beer. Use pry-off or flip-top bottles and press each cap on firmly.
• Conditioning too cold. Bottles left somewhere cold barely carbonate at all. If they are still flat at two weeks, move them somewhere warmer and give them another week before you decide the batch failed.

None of these are talent problems. They are procedure, and every one of them is easy to avoid once you know it is coming.