How is cider ABV calculated?

The standard homebrew formula is ABV ≈ (OG − FG) × 131.25, where OG is the original gravity of the juice (plus any added sugar) and FG is the final gravity after fermentation. The difference reflects how much sugar the yeast converted to alcohol and CO₂.

What gravity is plain apple juice?

Pure apple juice usually starts around 1.045 to 1.052, which corresponds to roughly 11 to 13 Brix. That yields a cider of about 5 to 6.5 percent ABV if fermented dry, without adding any sugar.

How much does added sugar raise ABV?

Each 17 grams of sugar per litre raises gravity by about 0.007 to 0.008 and adds roughly 1 percent ABV when fully fermented. The calculator adds your sugar to the starting gravity so the final ABV reflects the boosted juice.

Why do dry ciders finish below 1.000?

Apple juice contains little unfermentable extract, so cider yeast can consume nearly all the sugar. Because alcohol is less dense than water, a fully dry cider can finish at or below 1.000, sometimes around 0.996, which increases the OG−FG difference and the ABV.

Can I enter Brix instead of gravity?

Yes. Switch the input to Brix and the tool converts it to specific gravity with the standard formula before calculating. Remember a refractometer Brix reading is only valid for the starting juice — after fermentation, alcohol distorts it, so measure FG with a hydrometer.

What is the Cider ABV Calculator?

Compute hard cider ABV from apple juice starting gravity (or Brix) and final gravity. Supports added sugar to boost ABV and accounts for the low residual extract of dry ciders. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Cider ABV Calculator

Name: Cider ABV Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

The Cider ABV Calculator works out the alcohol content of hard cider from the starting gravity of the apple juice and the final gravity after fermentation. It supports added sugar to boost strength and handles the very dry finishes typical of cider.

How it works

Cider ABV uses the same gravity-difference formula as beer:

ABV ≈ (OG − FG) × 131.25

OG is the original gravity of the juice (plus any sugar you add) and FG is the gravity once fermentation is complete. The constant 131.25 converts the gravity drop into percent alcohol by volume.

If you enter Brix instead of gravity, the tool converts with the standard relationship:

SG = 1 + (Brix ÷ (258.6 − (Brix ÷ 258.2) × 227.1))

Adding sugar

Each 17 g of sugar per litre raises gravity by roughly 0.0078 and adds about 1% ABV when fully fermented. The calculator adds your sugar contribution to the juice’s starting gravity before computing alcohol, so you can plan a stronger cider.

Worked example

Supermarket apple juice reading 1.050 ferments out to a dry 0.998:

ABV ≈ (1.050 − 0.998) × 131.25 ≈ 6.8%

Add 34 g/L of sugar and the starting gravity rises to about 1.066, pushing the same dry finish to roughly 8.9% ABV — a much stronger cider.

Cider vs beer: what makes the ABV calculation different

The formula is the same as for beer, but cider has a characteristic that catches first-time brewers off guard: apple juice contains very little unfermentable extract (dextrins, proteins, the substances that give beer body). Almost all of apple juice’s dissolved solids are fermentable sugars. This means a cider yeast with good attenuation can convert virtually everything, producing a final gravity that is at or below 1.000.

Because alcohol is less dense than water, a completely dry cider can finish around 0.996–0.998 SG on a hydrometer — readings that would indicate an impossible “over-attenuation” in beer but are perfectly normal in cider. The OG − FG difference is consequently larger, which is why even a modest-gravity apple juice (1.045–1.052) can ferment into a 5–7% cider.

How gravity relates to Brix and sugar content

Apple growers and juice producers often measure sugar in Brix, which is the percentage of sugar by weight. A Brix reading on fresh-pressed juice and a specific gravity reading are two ways to express the same thing. The conversion is approximate:

11 Brix ≈ 1.045 SG (about 5.9% ABV potential)
13 Brix ≈ 1.052 SG (about 6.8% ABV potential)
15 Brix ≈ 1.061 SG (about 8.0% ABV potential)

Refractometers (the hand-held lens instruments common in orchards) read in Brix and are ideal for measuring fresh juice before fermentation. After fermentation begins, alcohol changes the refractive index, making a refractometer unreliable for final gravity. Always switch to a hydrometer for FG measurement.

Sugar additions and their effect

Adding granulated sugar (sucrose), honey, or juice concentrate before fermentation raises the starting gravity and therefore the potential ABV. Sucrose ferments completely, contributing no body or flavour, which is why it is commonly used to hit a target strength without sweetening the cider. Honey contributes trace flavour compounds and is the choice for craft cyser (apple-honey cider). Apple juice concentrate adds both sugar and apple flavour, which suits more aromatic styles.

A practical planning approach:

Measure the juice OG with a hydrometer before adding anything.
Enter the juice OG into this calculator and see what ABV you get with full attenuation.
If you want a higher target, calculate how much sugar to add by working backwards from the desired OG, remembering each 17 g/L adds approximately 0.007 SG.
Add the sugar, stir until dissolved, and re-measure OG to confirm.

Notes

Cider has little unfermentable extract, so dry ciders often finish at or below 1.000; do not be surprised by a sub-1.000 FG.
Brix is only valid for the starting juice; alcohol distorts a refractometer, so always measure final gravity with a hydrometer.
Higher ABV ciders ferment more slowly and may need a more alcohol-tolerant yeast strain.
Pasteurised supermarket apple juice is a convenient and consistent starting material; cloudy or fresh-pressed juice varies more in gravity and typically produces a more complex flavour.