Priming Sugar Calculator
Enter your batch volume, the warmest temperature the beer reached after fermentation, and a target carbonation level — get the exact grams of priming sugar for bottle conditioning, in corn sugar, table sugar, DME, or honey. Built on sugar = (target − residual CO2) × 1.96 × volume ÷ yield by a former New Belgium yeast specialist.
CO2res = 3.0378 − 0.050062·T + 0.00026555·T² (T in °F) · sugar grams = CO2 to add ÷ yield. Yields: corn 0.50, table 0.54, DME 0.42, honey 0.46 g CO2/g sugar.
Prime for the carbonation you want — not more, not less.
Priming sugar grams = the CO2 you still need to add, divided by how much CO2 that sugar actually yields. Bottle conditioning works by giving the yeast still in suspension one last measured dose of sugar to ferment, trapping the CO2 it produces in the sealed bottle. Too little sugar and the beer is flat; too much and you've built a bottle bomb. This tool does the residual-CO2 math for you and hands back the grams — or ounces — of corn sugar, table sugar, DME, or honey to add at bottling, tuned to your exact volume, temperature history, and style target.
Everything runs client-side. Nothing is stored, nothing is sent — change any input and the result updates live.
The priming sugar formula, explainedThe math behind the number.
Residual CO2: what's already dissolved in the beer
Beer isn't flat before you prime it — fermentation itself dissolves CO2 into the beer, and how much depends entirely on temperature. Warmer beer holds less dissolved CO2; colder beer holds more. That relationship is the standard residual-CO2 polynomial, with temperature in °F:
CO2res = 3.0378 − 0.050062·T + 0.00026555·T²
CO2 to add: the gap between target and residual
Once you know what's already dissolved, the sugar only needs to supply the difference between that and your target carbonation level. One volume of CO2 per liter of beer is a fixed physical quantity — 1.96 grams per liter — so the gap converts directly to a mass of CO2 the priming sugar must produce:
CO2_add_g = (target_vol − CO2res) × 1.96 × volume_L
Sugar grams: CO2 needed ÷ what the sugar yields
Different priming sugars don't produce the same CO2 per gram fermented — a gram of pure dextrose ferments differently than a gram of DME with its unfermentable dextrins, or a gram of honey with its water content and variable sugar profile. Divide the CO2 you need by the sugar's yield factor to get the grams to weigh out:
sugar_g = CO2_add_g ÷ yield
corn sugar (dextrose) yield = 0.50
table sugar (sucrose) yield = 0.54
DME yield = 0.42
honey yield = 0.46
5 gal batch (18.93 L), warmest post-ferment temp 68°F, American ale target 2.4 volumes, corn sugar.
CO2res = 3.0378 − 3.404 + 1.227 ≈ 0.861 volumes already dissolved at 68°F.
CO2 to add = (2.4 − 0.861) × 1.96 × 18.93 ≈ 57 g of CO2 still needed.
Corn sugar = 57 ÷ 0.50 ≈ 114 g (about 4.0 oz) — dissolved in a small amount of boiled water and racked into the bottling bucket.
When the standard number is wrong.
Priming sugar math looks simple, and it is — right up until you feed it the wrong temperature or ignore the fermentability of your sugar source. Here's where that costs you.
Residual CO2 is set by the warmest temperature since fermentation — not serving temp
This is the single most common input error, and it's the one that causes real damage. Residual CO2 is fixed by the warmest temperature the beer reached after fermentation finished — not the temperature it's sitting at right now, not the fridge, not serving temp. A beer that fermented at 68°F and was later cold-crashed to 34°F still carries roughly 68°F worth of dissolved CO2, because that CO2 got locked in before the beer ever got cold. Cold crashing doesn't release it — it just makes more room in solution that the beer hasn't had time to re-absorb.
Plug in the fridge or cold-crash temperature here and the calculator will tell you residual CO2 is much higher than it actually is, which under-primes the math — and the classic result runs the other direction in practice, because brewers who eyeball this without a calculator tend to guess low on residual CO2 and add a full priming dose on top of beer that already has more dissolved gas than expected. Either direction of error on this input is exactly how bottle bombs happen. Use the high-water-mark temperature, always.
Style targets span 2–3× — a generic number flattens one style and over-gasses another
A British bitter at ~1.6 volumes and a hefeweizen at ~4.2 volumes are both textbook-correct — for their style. Default to a generic "2.4 for everything" and the bitter comes out gassy and thin-feeling while the hefeweizen comes out under-carbonated and flat-tasting, missing the fluffy, effervescent mouthfeel that's part of the style's identity. Pick the target off the style, not off habit.
DME and honey are not 100% fermentable — their yields are lower and more variable
Corn sugar and table sugar are nearly pure fermentable sugars, so their CO2 yield per gram is predictable batch to batch. DME and honey are not — DME carries unfermentable dextrins from the mash, and honey's sugar content and moisture vary by source and season. Their yield factors (0.42 and 0.46 here) are reasonable averages, but treat them as estimates, not certainties. When precision matters — a delicate style, a beer already close to bottle-strength carbonation — prefer corn or table sugar for the predictability, and hold DME or honey for when the flavor contribution is the point.
Safety: bottle strength and fermentation stability
Standard beer bottles are rated for roughly 2.5–3.0 volumes of CO2. Above about 3.5 volumes you need genuinely pressure-rated bottles — Belgian or Champagne style, with a wired cage or heavy punt — not standard longnecks. And priming math assumes the beer has finished fermenting: if fermentation stalled early or you're bottling before a stable final gravity, the yeast still has unfermented sugar to work through in the bottle in addition to the priming sugar you just added. That stacked, uncontrolled sugar load is exactly how you get gushers or bottle bombs. Confirm a stable FG over several days before you prime and bottle — check it with the attenuation calculator if you're not sure fermentation actually finished.
Notes from the labAt New Belgium, residual CO2 wasn't a guess — it was measured, because getting it wrong at scale doesn't mean one gusher, it means a pallet of them. The habit that carries over to five-gallon batches: write down the warmest temperature your beer sees after fermentation ends, the day it happens, not the day you bottle three weeks later after it's been sitting in a cool corner. Homebrewers lose this number constantly — they remember the cold-crash temp because that's what they see right before bottling, and forget the number that actually matters. The beer remembers its warmest day. Your priming math should too.
Track carbonation against how the batch actually turns out.
Priming sugar is a prediction, same as any other batch calculation. The value shows up when you log it against attenuation, temperature, and how each batch actually carbonates — and see which combinations produce clean, safe, on-style beer every time. That's what a QC dashboard does automatically.