Priming Sugar Calculator
How much sugar to add at bottling, accounting for the CO₂ your beer is already holding at its current temperature.
19 L is a standard 5 US gallon batch.
Use the highest temperature the beer reached after fermentation finished.
How this was worked out
residual CO₂ = 3.0378 − (0.050062 × 70) + (0.00026555 × 70²) = 0.835 volumes
still needed = 2.4 − 0.835 = 1.565 volumes
CO₂ mass = 1.565 × 19 L × 1.9635 g/L = 58.4 g
sugar = that × 2.0468 ÷ 0.91 = 131.3 g
Dextrose monohydrate; 91% fermentable sugar by weight, the rest water.
| Style | Volumes | Corn sugar (dextrose) at your volume & temp |
|---|---|---|
| British-style ales | 1.5–2 | 77 g |
| Porter, stout | 1.7–2.3 | 98 g |
| Belgian ales | 1.9–2.4 | 110 g |
| American ales and lager | 2.2–2.7 | 136 g |
| European lagers | 2.2–2.7 | 136 g |
| Lambic | 2.4–2.8 | 148 g |
| Fruit lambic | 3–4.5 | 245 g |
| German wheat beer | 3.3–4.5 | 257 g |
Table shows the sugar needed to hit the midpoint of each style range at 19 L and 70 °F. Residual CO₂ at this temperature is 0.83 volumes.
Why temperature drives the answer
Bottle conditioning is a small, deliberate second fermentation. You add a measured amount of sugar, the yeast still in suspension eats it, and because the bottle is sealed the CO₂ it produces has nowhere to go but into solution. The arithmetic is about how much CO₂ you still need — and that depends on how much is already there.
Beer holds dissolved CO₂ in proportion to how cold it is. That is why the calculation starts by working out residual CO₂ from your temperature and subtracting it from your target, rather than treating every beer as though it started flat.
Worked example
19 litres of beer at 70 °F, primed with corn sugar to 2.4 volumes.
At 70 °F the beer already holds 0.83 volumes, so 1.57 volumes still have to be produced — which needs 131 g (4.63 oz) of corn sugar.
The same beer at 45 °F already holds 1.32 volumes, so it needs only 90 g — about 31% less sugar for identical carbonation.
Residual CO₂ by temperature
| Beer temperature | CO₂ already held | Corn sugar for 2.4 vols in 19 L |
|---|---|---|
| 40 °F | 1.46 vols | 79 g |
| 50 °F | 1.20 vols | 101 g |
| 60 °F | 0.99 vols | 118 g |
| 65 °F | 0.91 vols | 125 g |
| 70 °F | 0.83 vols | 131 g |
| 75 °F | 0.78 vols | 136 g |
| 80 °F | 0.73 vols | 140 g |
Common mistake
Bottling a beer that has not actually finished. Priming sugar assumes the only fermentables in the bottle are the ones you put there. If fermentation was merely slow rather than complete, the leftover sugar ferments too, and the combined CO₂ can exceed what the glass is rated for. Stable gravity readings several days apart, not elapsed time, are what tell you it is done.
Keep going
- Priming assumes fermentation is complete; checking attenuation first is what stops a still-fermenting beer being bottled. Attenuation Calculator
Frequently Asked Questions
Why does the beer's temperature change how much sugar I need?
Because beer already holds dissolved CO2 from fermentation, and how much it holds depends on temperature. Cold beer retains more. The calculator subtracts that residual from your target, so a beer sitting at 40 °F needs far less priming sugar than the same beer at 75 °F.
Which temperature should I enter — current, or fermentation?
The highest temperature the beer reached after fermentation finished. CO2 driven off at that peak does not come back when the beer cools again, so the peak is what determines what is actually still in solution.
Why does corn sugar need more grams than table sugar?
Two separate reasons that compound. Chemically, sucrose yields four molecules of CO2 per molecule while dextrose yields two, so dextrose needs more weight per gram of CO2. On top of that, corn sugar as sold is dextrose monohydrate — about 91% fermentable sugar, the rest water. Both effects push the corn sugar figure up.
What happens if I overshoot the target?
Overcarbonated beer at best gushes and at worst bursts bottles. The risk rises sharply if fermentation had not truly finished when you bottled, because the remaining fermentables add to whatever priming sugar you put in. Confirm stable gravity readings over several days before bottling.
Can I bottle straight from the fermenter without priming?
Only if the beer still has active fermentation left, which is what traditional methods like krausening rely on. Priming exists precisely because a finished beer has no fermentables left to produce carbonation on its own.
Sources. The residual CO₂ equation, the carbonation ranges by style, and the sugar purity figures are from Brewer's Friend's priming calculator, retrieved 19 September 2026. The grams-of-sugar-per-gram-of-CO₂ figures are not from that source — they are derived here from fermentation stoichiometry and the molar masses of sucrose, dextrose and CO₂, and the derivation is shown in the result panel rather than presented as sourced. This is a calculation tool for homebrewing and says nothing about consumption.
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