Cider ABV Calculator

A refractometer measures how much light bends when passing through a liquid. Before fermentation this works perfectly for measuring sugar concentration. After fermentation, alcohol in the wash bends light differently to water — making the reading appear lower than the actual gravity. If you use the raw refractometer reading as your FG you will overestimate your ABV.

This calculator applies the Terrill correction formula, which uses both the original Brix reading and the post-fermentation apparent Brix to recover the true final gravity:

Where Ri = initial Brix (OG reading) and Rf = apparent final Brix (post-fermentation refractometer reading). This is the most widely accepted correction formula for homebrewing and home distilling.

Most hydrometers are calibrated at 20°C (68°F). If your sample is warmer, the liquid is less dense and the hydrometer floats higher, giving a reading that is lower than the true gravity. The correction runs about +0.001 SG per 5°C just above calibration temperature and grows with the gap, reaching roughly +0.006 SG at 40°C. This calculator applies the polynomial correction formula for accurate results across a wide temperature range.

The sugar in apple juice is almost entirely fructose, glucose and sucrose, all of which cider yeast ferments completely. There is no mash step and no dextrin, so unless you deliberately halt it, a cider ferments to dryness.

That means a finished dry cider usually lands between 0.996 and 1.002, and readings below 1.000 are routine rather than a sign of trouble. If you want residual sweetness you have to stabilise and back sweeten after fermentation, not rely on the yeast stopping on its own.

Typical range: original gravity 1.045 to 1.060 for straight pressed juice, giving roughly 6 to 8% ABV. Juice from dessert apples sits at the lower end, while cider-specific varieties and concentrate can push higher.

Apple juice also carries less nitrogen than grape must, so a slow or stalled cider fermentation is frequently a nutrient problem rather than a yeast-strain problem.

Apparent attenuation tells you what percentage of the available sugars have been fermented. Fresh apple juice ferments close to fully dry with most cider yeasts, so expect apparent attenuation of 95-100% for a standard dry cider.

A dry cider typically shows apparent attenuation above 95%, and often reads above 100% because the final gravity drops below 1.000. Sustained attenuation below 80% on a cider usually means the juice was nitrogen poor or the temperature dropped mid fermentation.