Wine Lab — Wine Making Chemistry Suite

Molecular SO2 is the active, antimicrobial form of free sulfur dioxide — the only form that actually protects wine from spoilage microbes and oxidation. Wine pH controls how much of your free SO2 exists in this active form: at pH 3.0 about 6% is molecular, at pH 3.5 only ~2%, and at pH 4.0 less than 1%. The relationship is molecular SO2 = free SO2 ÷ (1 + 10^(pH − 1.81)). That is why two wines with identical free SO2 readings can have very different levels of protection — and why high-pH wines need far more sulfite. This calculator computes your current molecular SO2 and the free SO2 needed to hit the standard targets (0.8 ppm for whites, 0.5 ppm for reds). For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

It depends on your wine’s pH and current free SO2, not on a fixed recipe. This wine sulfite calculator — a sulfite calculator for wine built on the pH equilibrium, not guesswork — takes your target free SO2 (or computes it from the molecular-SO2 mode: e.g. 40 ppm at pH 3.5 for 0.8 ppm molecular in a white), your measured free SO2, and your batch volume, then converts the deficit into grams of potassium metabisulfite, teaspoons (1 tsp ≈ 5.5 g), and the number of Campden tablets (0.44 g and 0.55 g sizes). A common rule of thumb is that roughly half of added SO2 becomes bound, so only about half shows up as free SO2. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

A 0.44 g sodium-metabisulfite Campden tablet contributes roughly 297 mg of SO2; in one US gallon (3.785 L) that is about 78 ppm of total SO2. The classic rule of thumb — one tablet per gallon gives ~50 ppm — reflects that only part of the dose remains as free SO2 after binding. Larger 0.55 g tablets contribute about 372 mg of SO2 each. Rather than guessing, use the sulfite dosing mode with your target ppm: it tells you the exact tablet count for your batch. Note that some tablets are made with potassium metabisulfite instead of sodium, which releases slightly less SO2 per gram (57.5% vs 67.6%). For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

Chaptalization is adding sugar to grape must before or during fermentation to raise the potential alcohol. Wondering exactly how much sugar to add to wine? The wine-lab chaptalization mode shows three published formulas side by side so you can compare: the standard 17 g of sugar per liter per °Brix, a conservative 10 g/L per °Brix, and the 1.5 oz per gallon per °Brix formula (equivalent to ~11.2 g/L per °Brix). For example, raising 25 L from 18 to 22 °Brix needs 1,700 g by the 17 g/L formula but only 1,000 g by the 10 g/L formula — a real disagreement worth seeing before you add sugar. Chaptalization is restricted or illegal for commercial wine in some regions (including parts of the EU); home-winemaking rules vary, so check your local regulations. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

Potential alcohol (PA) estimates the ABV a must could reach if fermented fully dry: PA = (Brix × 0.5765) − 0.65. A must at 22 °Brix therefore has about 12.0% potential alcohol, and 24 °Brix about 13.2%. This is the standard oenological relationship (Boulton; Zoecklein); real results vary with yeast strain, fermentation temperature, and how dry the wine finishes. If you already have hydrometer readings, use ABV = (OG − FG) × 131.25 instead — the tool’s converter handles both, plus SG ↔ °Brix ↔ °Plato conversions.

Decide your target total acidity (TA) first — typical targets are 6–7 g/L for dry whites and 5.5–6.5 g/L for reds (expressed as tartaric). Then acid needed = (target TA − current TA) × volume in liters, in grams. Example: 25 L at 4.5 g/L raised to 6.5 g/L needs 50 g of tartaric acid (~9 tsp). Tartaric is the standard choice for wine because it is the grape’s natural acid and the most stable; citric can add a citrus note and feed spoilage bacteria, while malic is softer but can invite malolactic activity. Add acids before or during fermentation where possible, in stages, and re-measure — it is easy to overshoot. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

Pearson’s square finds the proportions of two wines needed to hit a target value (ABV, Brix, or TA). Put the target in the middle, the two wine values at the corners: parts of wine A = |value B − target|, parts of wine B = |value A − target|. To blend a 12% and a 14% wine to 12.8%, you need (14−12.8)=1.2 parts of the 12% wine and (12.8−12)=0.8 parts of the 14% wine — a 60:40 ratio. The tool also computes the plain weighted average for any two (or more) batches: e.g. 10 L at 12% plus 10 L at 14% gives 20 L at 13%. Blend only finished, stable wines, and always bench-trial a small sample before committing the batch.

Yes — this wine dilution calculator uses the standard amelioration equation: water to add = volume × (current Brix ÷ target Brix − 1). For example, 20 L at 26 °Brix diluted to 23 °Brix needs about 2.6 L of water (~11.5% of the final volume). In the US, TTB rules cap water added in amelioration at 35% of the total volume for commercial wine, and many winemakers consider anything over ~10–15% a quality compromise because it dilutes flavor, acid, and tannin along with sugar. If you dilute significantly, consider acidulating the water to match the must’s acidity. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

First stabilize: potassium sorbate (plus sulfite at the correct pH-based level) so the added sugar does not restart fermentation in the bottle. Then sugar needed ≈ Δ°Brix × 10 g/L × volume. For 20 L raised from SG 0.998 to 1.010 that is about 617 g of table sugar, or ~752 g of honey (honey is ~82% sugar). Adding sugar adds volume, which dilutes the alcohol slightly — the calculator shows the corrected ABV (e.g. 12.0% → ~11.8% in that example). Add sweetener in stages and taste; you can always add more, but you cannot take it out. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

The standard home-winemaking dose is 0.5–0.75 g of potassium sorbate per US gallon (roughly 1/2 tsp per gallon; 1 tsp ≈ 2.3 g), always combined with sulfite at the proper pH-based free-SO2 level. Sorbate does not kill yeast — it only stops yeast cells from reproducing — so the wine must be clear and fermentation fully finished first. Never use sorbate in a wine that went through malolactic fermentation: lactic bacteria convert it into a compound that smells like geraniums. The US legal limit is 300 mg/L sorbic acid equivalent. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

A common home-winemaking rate is about 1 g of DAP (diammonium phosphate) per US gallon of must, often split between pitch and the 1/3-sugar-break; complex nutrients like Fermaid-K run at a similar 1 g/gal, Fermaid-O around 1.5 g/gal. For rehydration, Go-Ferm is dosed at 1.25× the yeast weight (e.g. 6.25 g for a 5 g yeast packet). The tool converts your batch size into grams and teaspoons for DAP, Fermaid-K, Fermaid-O, and Go-Ferm. These are planning estimates — high-Brix musts and low-nutrient fruit wines need more, and over-feeding DAP can leave harsh or sulfide off-flavors. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

25 liters fills 33.3 standard 750 mL bottles (33 full bottles plus ~250 mL) — the wine bottle calculator mode above handles any batch volume in liters, US gallons, or imperial gallons, plus magnums and half-bottles. UK alcohol units are calculated as ABV% × milliliters ÷ 1000, so a 750 mL bottle at 12% ABV contains 9 units, and the whole 25 L batch at 12% contains 300 units.

Use the built-in converter: °Brix is percent sugar by weight (refractometer/hydrometer scale), specific gravity is density relative to water, and °Plato is the brewing-industry twin of Brix (identical within ~0.05 for wine). The tool uses the ASBC polynomial: Brix = ((182.4601×SG − 775.6821)×SG + 1262.7794)×SG − 669.5622, e.g. SG 1.092 ≈ 22 °Brix. Note: refractometers read inaccurately once alcohol is present — use a hydrometer (or a refractometer correction) for fermenting or finished wine.

Free SO2 is the unbound portion (molecular SO2 + bisulfite) that you measure with a test kit; only the molecular fraction is antimicrobial. Total SO2 is free plus bound SO2 (bound to acetaldehyde, sugars, etc.) and is what regulators limit — e.g. the EU caps total SO2 at 150 mg/L for dry reds and 200 mg/L for dry whites, the US at 350 mg/L. Free SO2 above ~50 ppm can be tasted as a burnt-match note, which is another reason to dose by molecular-SO2 target rather than chasing a flat free-SO2 number at high pH. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.

Yes — private by construction. This is a single self-contained page with zero external requests: no analytics, no fonts, no CDNs, no servers. Every calculation runs locally in your browser with JavaScript, and your batch volumes, pH readings, and recipes never leave your device. It works offline once loaded.

No — treat every result as a planning estimate. The formulas are standard oenological relationships (Boulton’s Principles and Practices of Winemaking; Zoecklein’s Wine Analysis and Production; the pH/SO2 equilibrium table from the rec.crafts.winemaking FAQ), but real wine deviates: sulfite binding varies by wine, teaspoon weights are approximate (always prefer a 0.1 g scale), and legal additive limits differ by country and wine style. Verify critical additions with a certified lab or oenologist, especially for wine you sell or share. Sulfites are allergens — labeling is required in many jurisdictions. For home winemaking education. Additive legal limits vary by country — verify with local regulations. Sulfites are allergens (labeling required in many jurisdictions). Not professional oenological advice; verify critical additions with a certified lab/oenologist.