How much priming sugar for bottling?

What the number means

Bottle conditioning carbonates beer with a little fermentable sugar. You stir the sugar into the finished beer, bottle it, and the yeast left in suspension ferments it in the sealed bottle. The CO2 it makes cannot escape, so it dissolves in the beer. Carbonation is counted in volumes of CO2: one volume is one liter of gas, measured at 0 °C and normal air pressure, dissolved in each liter of beer. A British bitter sits near 1.5 to 2 volumes, an American pale ale near 2.2 to 2.7, a German wheat beer at 3.3 to 4.5 (ranges from Palmer's How to Brew).

The method

Step 1. Residual CO2. Fermented beer already holds CO2, more when it is cold. The formula used by Brewer's Friend is 3.0378 − 0.050062 T + 0.00026555 T² (T in °F; the calculator applies it from 32 to 90 °F). Step 2. CO2 to add is your target minus the residual. Step 3. Sugar is the CO2 to add times the grams of sugar that make one volume in your batch.

The grams per volume come from the chemistry of fermentation and are our own derivation, checked against a published table. One liter of CO2 gas at 0 °C weighs about 1.977 g. Fermentation turns one molecule of glucose into two of CO2; sucrose splits first into glucose and fructose, so it gives four. Corn sugar is glucose with a molecule of water (dextrose monohydrate, 198.17 g/mol, about 91% glucose), table sugar is sucrose (342.3 g/mol) and anhydrous dextrose is 180.16 g/mol. That makes one volume of CO2 in each liter of beer need 3.84 g of table sugar, 4.45 g of corn sugar or 4.05 g of anhydrous dextrose. The Brew Your Own priming chart for 5 gallons agrees within about 2%. For dry malt extract we take 1.5 times the table sugar, following Brewer's Friend, which assumes that 68% of extract ferments; that figure is the calculator maker's assumption, so treat the DME answer as less certain.

Worked example. 5 gallons of beer that peaked at 68 °F, target 2.4 volumes: residual 0.86, so 1.54 volumes must come from sugar. With corn sugar at 4.45 g per liter per volume, that is 1.54 × 4.45 × 18.93 L = 130 g, or 4.6 oz.

Limits and common mistakes

Using the wrong temperature. The right one is the warmest the beer got after fermentation, not the temperature when you bottle. Cold crashing does not put the lost gas back.

Using the wrong volume. Use the beer that goes into the bottling bucket, after the trub is left behind, not the batch size on the recipe. Adding sugar for 5 gallons to 4.5 gallons of beer puts in 11% too much sugar for the beer you have.

Two sources for the residual CO2 disagree a little. The Brewer's Friend polynomial gives 1.20 volumes at 50 °F and the Brew Your Own table 1.15; at 77 °F they give 0.76 and 0.728. The difference is small next to the normal variation in how much yeast and fermentable sugar are in a bottle.

Bottling too early. Sugar that is already in the beer from an unfinished fermentation adds to the priming sugar. Palmer says ales are usually ready to bottle in 2 to 3 weeks, once there are few if any bubbles through the airlock, and that fermentation can stop for a few days and start again with a change in temperature.

Frequently asked questions

How much priming sugar do I need for a 5 gallon batch?

It depends on how much carbonation you want, how warm the beer got, and which sugar you use. For 5 gallons at 68 °F carbonated to 2.4 volumes of CO2, you need 130 g (4.6 oz) of corn sugar, 112 g (3.9 oz) of table sugar or 168 g (5.9 oz) of dry malt extract. John Palmer's own rule of thumb is 4 ounces (3/4 cup) of corn sugar for a 5 gallon batch, which is about 2.2 volumes of CO2 at 68 °F by this calculation.

Why does the temperature of the beer matter?

Beer holds some CO2 from fermentation, and colder liquid holds more of it. Brewer's Friend publishes the residual CO2 as 3.0378 − 0.050062 T + 0.00026555 T², with T in °F: 0.86 volumes at 68 °F, 1.20 at 50 °F. Use the highest temperature the beer reached after fermentation finished, not the temperature of your cellar, because gas leaves warm beer and does not go back when it cools. Brew Your Own prints a table that is a little lower (0.85 at 68 °F and 1.15 at 50 °F); the difference is 0.01 to 0.05 volumes, about 1 to 4 grams of sugar in 5 gallons. Palmer's book uses a nomograph for the same correction.

Is corn sugar the same as table sugar?

No. Corn sugar is dextrose (glucose) sold as the monohydrate, which is about 91% glucose by weight, and sucrose splits into two sugar molecules during fermentation, so a gram of table sugar makes more CO2 than a gram of corn sugar. By the chemistry, one volume of CO2 in 5 gallons needs about 73 g of table sugar, 84 g of corn sugar or 109 g of dry malt extract. Palmer says the same in words: ounce for ounce, cane sugar generates a bit more CO2 than corn sugar, and both carbonate more than malt extract.

How do I add the sugar?

Palmer's method is to boil the sugar in about 2 cups of water, let it cool, pour it into a sanitized bottling bucket and siphon the beer on top of it, with the outlet below the surface so the beer does not splash. He warns against putting a teaspoon of sugar in each bottle: it is slow, imprecise, can carbonate bottles unevenly (so some explode) and, because the sugar is not boiled, adds a risk of infection. Palmer also says not to let the beer splash at this stage, because you do not want to add oxygen.

What causes bottle bombs?

Almost always too much fermentable sugar in the bottle. Palmer's chapter on bottling warns that bottling before fermentation has finished makes beer over-carbonated, and that the pressure can exceed the strength of the bottle: ales are usually ready in 2 to 3 weeks, and fermentation can stop for a few days and restart with a change in temperature. Other causes are a measuring mistake, uneven mixing and using a carbonation level that the bottle was not made for. Homebrewers commonly treat 3 volumes of CO2 as the limit for ordinary beer bottles; we found no manufacturer rating, so treat that as a community rule. Store bottles in a place where a burst will do no harm and wear eye protection when you open a bottle you suspect.

Sources: John Palmer, How to Brew (free online edition, howtobrew.com), chapter 11 "Priming and Bottling": "When to Bottle", "What Sugar Should I Prime With?" and "Priming Solutions" (first edition, copy at web.archive.org, read October 28, 2026); Brew Your Own, Carbonation Priming Chart (byo.com); Brewer's Friend, Beer Priming Calculator (the residual CO2 polynomial and the DME assumption; a community tool, not a standard). The exact sugar-per-volume figures are our stoichiometric derivation. Neighbours: ABV calculator, strike water temperature calculator, yeast pitch rate calculator. How we check our calculators.