Campden Tablets vs Potassium Metabisulfite: How Much per Gallon

The standard home winemaking dose is one crushed Campden tablet per US gallon of must or wine. That is the rate printed on the Campden tablet listings we checked, and it is the rate given by NDSU Extension's home winemaking guide (reviewed in 2026), which equates one tablet per gallon with about 50 parts per million (ppm) of sulfur dioxide. The North Mountain Supply listing for its potassium Campden tablets puts the same dose at 75 ppm of total sulfur dioxide, so the exact number depends on the brand and on how you measure it.

Campden tablets and potassium metabisulfite powder are the same chemistry in two formats. Tablets are pre-measured for small batches; powder is cheaper and easier to dose for five gallons and up. Below you will find how many tablets to use for common batch sizes, the powder equivalent, when in the process to add sulfite, how wine pH changes the dose you need, and the mistakes that leave wine either unprotected or smelling of burnt matches.

What Campden Tablets Are

A Campden tablet is a compressed tablet of metabisulfite, the salt winemakers use to add sulfur dioxide (SO2) to must and wine. Once dissolved, it releases sulfur dioxide, which slows spoilage microbes, holds back wild yeast and protects the wine from oxidation. The Craft A Brew listing describes its tablets as a sterilant that suppresses wild yeast and spoilage organisms, and recommends adding a tablet to the must 24 hours before pitching yeast so the cultured yeast starts with no competition.

Potassium vs Sodium Campden Tablets

You will find two kinds on the shelf. Potassium Campden tablets are made of potassium metabisulfite, the form that NDSU Extension and most winemaking instructions name. Sodium Campden tablets are made of sodium metabisulfite and are sold for the same jobs: the Craft A Brew sodium tablets are labeled at one tablet per gallon, just like the potassium versions. Our suggestion: buy potassium for anything that goes into the wine and keep sodium for cleaning or sanitizing duties. Read the label on whatever you buy, because, as Clemson Cooperative Extension's Basics of Home Winemaking (2023) points out, each brand of Campden tablets has its own dosage ratio.

Why Winemakers Add Sulfite at All

Sulfite does three jobs in a home winery. Before fermentation it knocks back the wild yeast and bacteria that ride in on fresh fruit, which is why NDSU Extension recommends sulfiting juice made from fresh fruit. During aging it protects the wine every time you rack it and expose it to air. At bottling, together with potassium sorbate, it helps keep a sweetened wine from fermenting again in the bottle. If you start from store-bought juice or a commercial wine kit, follow the instructions that came with it, because the sulfite schedule can differ from a fresh fruit recipe.

How Many Campden Tablets per Gallon

At one tablet per US gallon, the math for common batch sizes is simple. Crush the tablets into a fine powder first; whole tablets dissolve slowly and unevenly.

If you need to sulfite water to sanitize equipment instead of wine, the dose is much higher. Virginia Cooperative Extension's guide HORT-213, Wine Making for the Home Gardener, gives four Campden tablets per quart of water, or a quarter teaspoon of potassium metabisulfite powder per quart, for a sanitizing solution.

Campden Tablets vs Potassium Metabisulfite Powder

Potassium metabisulfite powder, often shortened to K-meta, is the loose form of the same compound. It is the better choice once you make wine in five or six gallon batches, because you can dose any amount instead of counting tablets. The LD Carlson potassium metabisulfite listing gives a quarter teaspoon per six gallons as an additive, dissolved in warm water first.

To dose powder to a target instead of by the spoon, Oklahoma State University Extension's fact sheet on free sulfur dioxide (2024) gives the formula: multiply the ppm you want to add by the volume in liters, then divide by 0.57. The result is in milligrams of potassium metabisulfite. For a 5 gallon batch (about 18.9 liters) and a 50 ppm addition, that is 50 x 18.9 / 0.57, or roughly 1,660 milligrams: a little over one and a half grams. A kitchen scale that reads in tenths of a gram makes this easy; our sulfite calculator does the arithmetic for any batch size.

When to Add Campden Tablets

The extension guides cited here add sulfite at up to four points. The timing matters as much as the dose, because sulfite added at the wrong moment can stall the yeast you want to keep.

Before Fermentation: 24 Hours Before the Yeast

Add the crushed tablets to fresh fruit, crushed grapes or fresh-pressed juice, stir, cover loosely and wait. The Home Brew Ohio Campden listing says to add the tablets to the must 24 hours before pitching your wine yeast, and Clemson Extension uses the same 24 hour window before adding yeast. That pause lets most of the free sulfur dioxide dissipate so it no longer bothers the cultured yeast.

At Racking During Aging

Each racking exposes the wine to some air. NDSU Extension recommends adding Campden tablets or SO2 at every other racking, and the Virginia Cooperative Extension guide does the same: one crushed tablet per gallon at every other racking, because the tablet added at the start has broken down and needs replacing. Dissolve the powder in a splash of the wine and stir it in gently.

At Bottling, With Potassium Sorbate

If you plan to sweeten the wine, or it still has some residual sugar, NDSU Extension advises potassium sorbate to stop the yeast from multiplying again, and warns that skipping it can make bottles burst if fermentation restarts. Sorbate is normally used together with sulfite; the Craft A Brew listing describes its tablets as a preservative when paired with potassium sorbate on bottling day. Our guide to bottling and corking homemade wine covers the full bottling day routine.

For Sanitizing Equipment

A strong sulfite solution is a traditional sanitizer for carboys, airlocks and bottles. Use the sanitizing strength from the Virginia Cooperative Extension guide above, work in a ventilated room, and rinse or drain according to the product label. For bottles, NDSU Extension suggests a no-rinse sanitizing agent just before filling, which keeps your Campden tablets for the wine itself.

Free SO2, pH and Why One Tablet Is Not Always Enough

The tablet-per-gallon rule is a starting point. What actually protects wine is the small share of free sulfur dioxide that stays in the molecular form, and that share depends on pH. Oklahoma State University Extension explains that wine mostly sits between pH 3.0 and 4.0, where less than 10 percent of the free SO2 is molecular, and gives the free SO2 needed to reach 0.8 ppm of molecular SO2 at each pH:

The same fact sheet gives a recommended free SO2 range of 15 to 40 ppm in wine. In practice this means a crisp, acidic white at pH 3.2 needs far less sulfite than a soft red or a low-acid fruit wine at pH 3.7. If you own a pH meter or strips, measure first and use the sulfite calculator; if you do not, the one-tablet-per-gallon rule at the points above is the safe default that home winemaking guides use.

Common Campden Tablet Mistakes

Most sulfite problems in home wine come from a few habits that are easy to fix.

Pitching the Yeast Too Soon

Adding wine yeast right after the tablets puts it into the strongest free sulfite the batch will ever see. Wait the full 24 hours the labels and Clemson Extension call for, then add the yeast.

Not Crushing the Tablets

A whole tablet sinks and dissolves slowly, leaving one zone of the must heavily dosed and the rest barely touched. Crush it between two spoons, as the Craft A Brew listing suggests, dissolve the powder in a little warm water or wine, and stir it through the whole batch.

Overdosing

More is not safer. The Virginia Cooperative Extension guide warns that too much metabisulfite leaves a burnt match smell, while too little lets the wine oxidize. Count tablets carefully, weigh powder instead of guessing, and keep a log of every addition, a habit Oklahoma State University Extension also recommends.

Treating the Rule of Thumb as Exact

Brands state different ppm figures for the same one-tablet dose, and pH changes how much protection you get. For high-pH wines, low-acid fruit wines or anything you plan to age for a year or more, measure pH and dose to a target.