How much priming sugar for 5 gallons?
For a typical ale — 5 gallons to 2.5 volumes of CO₂, the beer having sat no warmer than 68 °F since it finished — it's 137 g of corn sugar, about 4.8 oz. The arithmetic has three parts, and the middle one is where every mistake lives:
sugar = (target − residual) × 1.96 g/L × liters ÷ CO₂ per gram of sugar · (2.5 − 0.86) × 1.96 × 18.9 ÷ 0.444 = 137 g
One "volume" is a liter of CO₂ per liter of beer — 1.96 g of gas. The beer already holds some from fermentation, so the sugar only has to make up the difference, and a gram of sugar makes a fixed amount of gas. That's it. The whole difficulty is knowing what the beer already holds.
Which temperature do you enter? The one everyone gets wrong
Beer out of a fermenter isn't flat. It holds whatever CO₂ stays dissolved at the warmest it's been since the yeast stopped — about 0.86 volumes at 68 °F, 1.5 at 38 °F. While fermentation is running, the yeast replaces whatever escapes, so the peak during fermentation doesn't matter. Once it stops, gas that leaves in a warm spell is gone for good; crashing the beer to 38 °F afterwards makes it able to hold more, but there's nothing left to make more.
The ranking calculators disagree about this. Brewer's Friend asks for "the fermentation temperature… but might also be the current temperature" and tells you to use judgment. BrewUnited asks for the temperature at bottling, with the right rule filed as "the only exception." Craft a Brew asks for the highest temperature "during fermentation" — the one that doesn't matter. Here is what each choice does to the same 5-gallon batch, when the beer's true warmest since finishing was 68 °F:
| You enter | Calculator assumes | Corn sugar | Beer actually ends at |
|---|---|---|---|
| 38 °F Cold-crash temperature | 1.52 vol residual | 82 g | 1.84 vol — flat |
| 50 °F Cellar | 1.20 vol residual | 109 g | 2.16 vol — flat |
| 68 °F Warmest after fermentation ended — the right one | 0.86 vol residual | 137 g | 2.50 vol |
| 75 °F Warm spell during active fermentation | 0.78 vol residual | 144 g | 2.58 vol |
| 80 °F Summer garage | 0.73 vol residual | 148 g | 2.63 vol |
5 gal, target 2.5 volumes, corn sugar. "Ends at" assumes the true warmest since fermentation ended was 68 °F. Computed by this page's engine.
The two ways to get it wrong are not symmetric. Enter the cold-crash temperature and you use 40% less sugar than you should — flat beer, annoying, safe. Enter a temperature warmer than the beer really reached after finishing and you over-prime, and that's the direction the glass cares about.
Think back over the beer's life after the airlock went quiet. Did it sit in a warm room for a week? Ride in a car? Get moved to the garage in August? The warmest of those is your number. If you genuinely don't know, use the fermentation temperature — it's usually close — and never a colder one. When in doubt, err warm on the temperature and low on the target: a slightly flat beer is a minor disappointment, and the other outcome isn't.
Priming sugar chart (printable)
Corn sugar by target and batch, warmest temperature 68 °F. The strip underneath gives the residual at other temperatures — use the calculator, or subtract the difference from your target and read the table at that.
| Target (vol) | 5 gal · 19 L | 5.5 gal · 21 L | 6 gal · 23 L | 10 gal · 38 L |
|---|---|---|---|---|
| 1.8 | 79 g · 2.8 oz | 86 g · 3 oz | 94 g · 3.3 oz | 157 g · 5.5 oz |
| 2.0 | 95 g · 3.4 oz | 105 g · 3.7 oz | 114 g · 4 oz | 191 g · 6.7 oz |
| 2.2 | 112 g · 4 oz | 123 g · 4.3 oz | 134 g · 4.7 oz | 224 g · 7.9 oz |
| 2.4 | 129 g · 4.5 oz | 142 g · 5 oz | 154 g · 5.4 oz | 257 g · 9.1 oz |
| 2.5 | 137 g · 4.8 oz | 151 g · 5.3 oz | 165 g · 5.8 oz | 274 g · 9.7 oz |
| 2.6 | 145 g · 5.1 oz | 160 g · 5.6 oz | 175 g · 6.2 oz | 291 g · 10.3 oz |
| 2.8 | 162 g · 5.7 oz | 178 g · 6.3 oz | 195 g · 6.9 oz | 324 g · 11.4 oz |
| 3.0 | 179 g · 6.3 oz | 197 g · 6.9 oz | 215 g · 7.6 oz | 358 g · 12.6 oz |
| Warmest since finishing | 40 °F 4 °C | 45 °F 7 °C | 50 °F 10 °C | 55 °F 13 °C | 60 °F 16 °C | 65 °F 18 °C | 68 °F 20 °C | 70 °F 21 °C | 75 °F 24 °C | 80 °F 27 °C |
|---|---|---|---|---|---|---|---|---|---|---|
| Residual CO₂ (vol) | 1.46 | 1.32 | 1.20 | 1.09 | 0.99 | 0.91 | 0.86 | 0.83 | 0.78 | 0.73 |
Table sugar: use 86% of the corn-sugar weight. DME: ×1.21. Honey: ×1.14. Residual from the standard fit to ASBC solubility data; sugar yields from stoichiometry. Computed by this page's engine.
Corn sugar vs table sugar vs DME vs honey
They all make the same gas by the same reaction — a hexose molecule ferments to two of alcohol and two of CO₂, 0.489 g of gas per gram of sugar. What differs is how much fermentable sugar a gram of the product contains. For the same 5-gallon batch:
| Sugar | CO₂ per gram | For 5 gal to 2.5 vol | Why |
|---|---|---|---|
| Corn sugar (dextrose) | 0.444 g | 137 g · 4.8 oz | Dextrose monohydrate — 9% of its weight is water of crystallization. |
| Table sugar (sucrose) | 0.514 g | 118 g · 4.2 oz | Inverts to two hexoses, taking up water for free — the most CO₂ per gram. |
| Dry malt extract | 0.366 g * | 166 g · 5.9 oz | About 75% fermentable; varies by maltster. Slower, and adds a little body. |
| Honey | 0.391 g * | 156 g · 5.5 oz | About 80% sugars, the rest water; varies by honey. Weigh it, never spoon it. |
* DME and honey are averages — real products vary by maltster and by honey. Corn and table sugar are exact from chemistry. Warmest 68 °F.
Every calculator we could check treats corn sugar as pure glucose. The bag is dextrose monohydrate — each molecule carries one of water, which is 9% of the weight and makes no gas. So a gram of corn sugar yields 0.444 g of CO₂, not 0.489, and this page asks for 10% more of it. Table sugar has no such water and inverts by taking some up for free, which is why it needs 14% less by weight than corn sugar despite being "the same thing." If another calculator's numbers have always worked for you, this is why ours read higher — and 9% is well inside any style's range.
How many volumes of CO₂ for each style?
| Style | Volumes | Corn sugar, 5 gal, mid-range | Bottle at 70 °F, top of range |
|---|---|---|---|
| British ales, cask-style | 1.5–2 | 74 g · 2.6 oz | 21 psi |
| Porter, stout | 1.7–2.3 | 95 g · 3.4 oz | 26 psi |
| Belgian ales | 1.9–2.4 | 108 g · 3.8 oz | 27 psi |
| American ales | 2.2–2.7 | 133 g · 4.7 oz | 32 psi |
| European lagers | 2.2–2.7 | 133 g · 4.7 oz | 32 psi |
| German wheat beer | 3.3–4.5 | 254 g · 9 oz | 61 psi — rated bottles only |
Ranges as published by Brewer's Friend and the BJCP. Warmest 68 °F. Pressure from the standard Henry's-law fit. Computed by this page's engine.
Bottle bombs: the number that decides whether the glass survives
Carbonation is a pressure, and pressure depends on temperature. A beer at 2.5 volumes sits at about 29 psi in a 70 °F room. Standard pry-off bottles are comfortable to about 3 volumes — 37 psi at that temperature. A German wheat beer at the top of its range, 4.5 volumes, is 61 psi in the same room: not a matter of opinion, and not a bottle you want to be near in a warm car.
- The beer must be finished. Two hydrometer readings, three days apart, identical. Priming a beer that's still fermenting adds your sugar on top of whatever it hasn't eaten yet, and no calculator can see that.
- Weigh, don't measure. "Three-quarters of a cup" varies by a third depending on how it's packed. A $10 kitchen scale removes the biggest error on this page.
- Dissolve and distribute. Boil the sugar in a cup or two of water, cool it, put it in the bottling bucket first and rack the beer onto it gently. Stir once, from the bottom, without splashing. Sugar dumped into bottles individually gives you a case with a few bombs in it.
- Above 3 volumes, use bottles rated for it — thick-walled Belgian or swing-top. Store the first two weeks somewhere a failure can't hurt anyone, and if a batch may be over-primed, chill it hard and open the bottles slowly.
The honest summary: this calculator's arithmetic is exact, its inputs aren't. The temperature is a memory, the residual formula is a fit, DME and honey vary by the bag. The margin that makes it safe anyway is choosing a sensible target and using a bottle rated for it — not the third decimal place of the sugar.