This priming sugar calculator sizes bottle-conditioning sugar: it reads the CO₂ already dissolved in your beer (from its warmest post-fermentation temperature), subtracts it from your target carbonation, and converts the gap into grams of corn sugar (dextrose) or table sugar (sucrose) for your batch size.

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The CO₂ You Already Have Is Half the Recipe

Beer leaves fermentation already carbonated — quietly holding roughly 0.8–1.2 volumes of dissolved CO₂ depending on temperature (cold beer holds more: at 68 °F the chart value interpolated here is ≈ 0.85 vol). Priming sugar only buys the DIFFERENCE to your target: the defaults (5 gal at 68 °F targeting a classic 2.5 vol) need 1.65 vol of new CO₂, which corn sugar supplies at 16.84 g per gallon per volume → 139 g (4.9 oz) — matching the venerable “¾ cup-ish corn sugar per 5 gallons” rule of thumb that the formula now explains instead of reciting. The sugar factors are stoichiometry, not folklore: fermenting dextrose monohydrate yields 0.444 g CO₂ per gram, sucrose 0.515 g/g (table sugar is the stronger gas source gram-for-gram, priced into its lower 14.54 factor), and a “volume” of CO₂ is one litre of gas (at standard conditions) per litre of beer — all of which the calculator chains so the number can travel across batch sizes, styles and sugars without new rules of thumb.

The safety paragraph is not decoration: over-priming sealed glass is the hobby's one genuinely hazardous arithmetic error. Respect bottle ratings (standard crown bottles ≈ up to 3.0 vol), verify fermentation is complete by stable hydrometer readings over 2–3 days before priming at all (unfinished beer + priming sugar stacks two CO₂ sources), and store conditioning bottles somewhere a failure is a mess, not an injury. Under-priming is merely sad; the calculator's precision exists so neither error is yours.

Worked Examples (Verified)

  • Defaults: residual 0.85 vol at 68 °F → need 1.65 → 139 g corn sugar (4.91 oz) for 5 gal at 2.5 vol.
  • Table sugar swap: same batch on sucrose → 14.54 × 5 × 1.65 = 120 g — less sugar, same gas (sucrose ferments to more CO₂ per gram).
  • Hefeweizen ambition: target 3.2 vol, beer at 70 °F (residual 0.83) → need 2.37 → corn sugar 16.84 × 5 × 2.37 = 200 g, in bottles rated for the pressure.

Priming Discipline

  • Temperature means the beer's WARMEST post-fermentation temperature: CO₂ escapes as beer warms, so a lager warmed to room temp for bottling holds room-temp residual, not lager-cold residual.
  • Uniform distribution is the whole safety game: syrup into the bucket first, rack beer onto it with a gentle swirl — never sprinkle dry sugar bottle-by-bottle unless weighing each (a “sugar cube per bottle” system with verified cube mass is the legitimate exception).
  • Confirm final gravity stability before priming (two readings, 2–3 days apart, unchanged) — the calculator assumes fermentation is done.
  • Condition at 65–75 °F ~2 weeks, then chill a test bottle 48 hours before judging: warm beer lies about carbonation (gas hides in the headspace until chilled into solution).
  • DME and honey prime too (factors differ — DME ~ more grams per volume due to unfermentables, honey ~85% fermentable sugars plus water) — this page prices the two pure sugars; treat alternatives with their own fermentability math.

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Frequently Asked Questions

How much priming sugar for 5 gallons of beer?

At typical ale conditions (beer ~68 °F, target 2.5 volumes): about 139 g (4.9 oz) of corn sugar or 120 g of table sugar. The amount moves with beer temperature (residual CO₂) and target carbonation — this calculator computes it from those inputs instead of reciting one batch's answer.

What are “volumes of CO₂”?

The volume of CO₂ gas (at standard temperature and pressure) dissolved in one volume of beer: 2.5 volumes means each litre of beer holds 2.5 litres' worth of gas. It's the carbonation unit of brewing specs and style guidelines — commercial lagers ~2.5–2.7, soda ~3.5–4, champagne ~5–6 (in pressure-rated glass).

Why does beer temperature matter?

Beer holds CO₂ in proportion to its coldest recent life but LOSES it when warmed: residual carbonation is set by the warmest temperature since fermentation (gas that left doesn't return). Cold-crashed beer that's warmed to 68 °F for bottling day has ~68 °F residual (≈0.85 vol), not the 1.1+ vol it held at 40 °F. Enter the warmest sustained temp, as the input label insists.

Corn sugar vs table sugar for priming?

Both ferment cleanly and completely at priming doses; the old “sucrose makes cider flavors” wisdom has not survived blind testing at these quantities. Sucrose yields more CO₂ per gram (0.515 vs 0.444 g/g), so you use less by weight (the calculator's factors encode this). Corn sugar dissolves marginally easier; table sugar is in every pantry. Choose by convenience, dose by the factor.

How long does bottle conditioning take?

About two weeks at 65–75 °F for most ales (yeast consuming ~5–10 g/L sugar and reabsorbing byproducts — the diacetyl cleanup is part of the wait), longer for high-gravity or lager strains, and high-ABV beers may need fresh yeast at bottling to carbonate at all. Chill 24–48 hours before opening: CO₂ equilibrates into cold beer, and the first bottle opened warm is a liar about the batch.

Can I over-carbonate and what happens?

Yes — excess fermentables (priming overdose, unfinished fermentation, infection with super-attenuating strains) pressurize bottles past their rating: gushers at best, bottle bombs at worst. Respect ~3.0 vol in standard bottles, verify final gravity stability, and if a batch shows early gushers, chill everything and vent carefully (gloves, eye protection, over a sink) — then drink it young rather than storing it warm.

What if I keg instead?

Force carbonation replaces sugar with a regulator: set pressure by temperature and target volumes on a carbonation chart (the residual-CO₂ physics is the same, delivery differs). “Keg priming” also exists — dose at roughly HALF the bottle rate (the keg's headspace and single-vessel geometry change the equilibrium, and a spunding valve refines it) — but bottle calculators like this one are written for glass; follow keg-specific guidance there.

Is this priming sugar calculator free?

Yes — free, instant, no sign-up. Enter batch gallons, beer temperature, target volumes and sugar type for the gram and ounce dose.