Free homebrew tools

Scale any homebrew recipe to your batch size

Q: How is ABV calculated from OG and FG?

The common homebrew formula is ABV ≈ (OG − FG) × 131.25. An original gravity of 1.055 finishing at 1.010 gives roughly 5.9% ABV.

Q: How much priming sugar do I need for bottling?

It depends on batch volume, target CO₂ volumes (around 2.4 for most ales) and beer temperature. The calculator uses corn (dextrose) sugar at 91% fermentability and gives grams for the whole batch.

Q: How much dry yeast should I pitch?

Pitch about 0.1 packets (11 g) of dry yeast per litre for normal-gravity beers, and roughly double above 1.060 OG. The calculator rounds up to whole 11 g packets.

Paste a recipe, set your batch size, and get every ingredient re-scaled instantly. Works for beer, cider, mead, kombucha & seltzer. No sign-up, nothing stored.

Built by the makers of the Fermentory recipe-scaler extension.

🍺 Recipe Scaler

Found a 20 L recipe but only brew 10 L? Drop the ingredient list in below.

Recipe is written for

You want to brew

Batch unit

Scale factor ×0.5

Paste ingredients — one per line

Scaled recipe

Brewing calculators

The same formulas built into the Fermentory extension — free to use here, no account needed.

ABV calculator

Original gravity (OG)

Final gravity (FG)

Yeast pitch rate (dry)

Batch size (L)

Original gravity

Priming sugar (bottling)

Batch (L)

Target CO₂ vol.

Beer temp (°C)

IBU (Tinseth)

Alpha acid %

Hops (g)

Batch (L)

Boil OG

Boil (min)

Do this automatically — on every recipe you find

The free Fermentory browser extension spots homebrew recipes on any page and lets you scale, save and shop them without copy-pasting into a calculator.

Auto-detects recipes on blogs, forums & recipe sites
One-click scale to your batch size — ingredients adjusted for you
Build a shopping list from any recipe
Save recipes & keep a brew journal (gravities, dates, notes)
100% local & private — no account, no tracking

＋ Add Fermentory to Chrome Free to install · optional one-time Pro upgrade

Homebrew scaling & calculator FAQ

How do you scale a homebrew recipe to a different batch size?

Divide your target batch size by the recipe's original batch size to get a scale factor, then multiply every ingredient by that factor. For example, taking a 20 L recipe down to 10 L gives a factor of 0.5, so 2.5 kg of malt becomes 1.25 kg. The scaler above does this for your whole ingredient list at once. Hop bitterness doesn't scale perfectly linearly, so re-check IBU with the calculator if you change the batch size a lot.

How is ABV calculated from OG and FG?

The common homebrew formula is ABV ≈ (OG − FG) × 131.25. So an original gravity of 1.055 finishing at 1.010 gives roughly 5.9% ABV. It's an estimate that's accurate enough for almost all homebrew beer, cider, mead and seltzer.

How much priming sugar do I need for bottling?

It depends on your batch volume, the target CO₂ level (around 2.4 volumes for most ales), and the beer's temperature, which determines how much CO₂ is already dissolved. The calculator above uses corn (dextrose) sugar at 91% fermentability. Add the sugar to the whole batch, not per bottle, for even carbonation.

How much dry yeast should I pitch?

As a rule of thumb for dry yeast, pitch about 0.1 packets (11 g) per litre for normal-gravity beers, and roughly double that above 1.060 OG. The pitch-rate calculator rounds up to whole 11 g packets so you're never under-pitching.

Is this free? Do you store my recipes?

The calculators on this page are completely free and run entirely in your browser — nothing you type is sent anywhere or saved. The Fermentory extension is also free to install (with an optional one-time Pro upgrade) and stores everything locally on your device. See our privacy policy.