A beer brewer picking up cider for the first time generally expects the gravity math to work exactly the same way, and mostly it does — but cider pushes the same formulas into territory beer almost never reaches, and the first time an experienced beer brewer sees the result, it can look like the calculator got something wrong. It didn't.
The number that looks broken but isn't
A dry cider starting at 1.050 OG and finishing at 0.998 FG — a completely normal, unremarkable result for a dry cider fermented with a wine or cider-specific yeast — computes to 104% apparent attenuation. Check it yourself. To a beer brewer, a number above 100% reads as an obvious error; attenuation is supposed to be a percentage of something, and percentages of a real quantity don't exceed 100. But the arithmetic is doing exactly what it's supposed to: (OG - FG) / (OG - 1) x 100 doesn't know attenuation is "supposed" to stay under 100%, it just computes the ratio it's given — and when FG drops below 1.000, that ratio genuinely can, and routinely does, exceed 100%.
Why FG can drop below 1.000 at all
Plain water reads 1.000 on a hydrometer by definition. A beer or cider containing only unfermented sugar and water will always read above 1.000, because dissolved sugar is denser than water. But dissolved alcohol is less dense than water — and once fermentation has consumed enough sugar and produced enough alcohol, that alcohol's lower density can pull the overall reading below 1.000 even with a small amount of unfermented extract still technically present. Cider reaches this point routinely because apple juice ferments highly cleanly and completely with the right yeast — there's comparatively little complex, less-fermentable extract left behind the way a beer's dextrin-rich wort typically has, so a dry cider's FG has real room to drop below water's own reading in a way most beer worts never approach.
Real attenuation tells the sensible-looking story
Run the same 1.050/0.998 pair through real attenuation instead — the Balling-formula-corrected figure that accounts for alcohol's density contribution separately from sugar's — and it comes out to a much more intuitive-looking 85.4%. Check the full result here, which reports both figures side by side on every result. This is a genuinely useful illustration of why real attenuation exists as a separate figure at all, covered in general terms on why real attenuation is always lower than apparent attenuation — cider just makes the underlying reason unmissable, where beer usually keeps it subtle.
A less extreme cider example, for comparison
Not every cider goes bone dry. An off-dry cider finishing at 1.006 from a 1.055 OG — still fairly dry by cider standards, but well short of the extreme example above — computes to 89.1% apparent attenuation and 72.6% real attenuation, both comfortably under 100% and closer to what a beer brewer's intuition already expects. Check it here. The gap between apparent and real is still there (16.5 points, a touch wider than typical beer-strength gaps), but nothing about the numbers looks broken the way the fully-dry example does.
ABV works completely normally either way
Despite the strange-looking attenuation figure, ABV itself behaves exactly as expected for the dry example: 6.83% ABV by the simple formula, 6.86% by the advanced one — two ordinary-looking numbers, computed from the identical OG/FG pair that produced the unusual attenuation figure. ABV is a direct function of the gravity drop itself, not a percentage that can exceed some notional ceiling, so it never produces the "how can this be over 100%" moment attenuation does on a very dry cider.
What carries over from beer brewing, and what doesn't
The ABV calculator, dilution and blending calculator, and priming sugar calculator all work identically on cider gravity readings — there's nothing beer-specific baked into any of that math. What doesn't carry over: there's no mash, so the strike water calculator and grain-bill concepts like diastatic power simply don't apply, since cider starts from pressed apple juice rather than converted grain starch. There's also no conventional IBU or SRM range for cider in most references — the style guideline reference lists cider entries honestly without inventing a bitterness or colour target that doesn't meaningfully exist for the category.
Starting gravity is a different conversation entirely
Beer's OG is set by a brewer's grain-bill and mash-efficiency choices — a genuine design decision with a wide practical range. Cider's OG is set almost entirely by the apples (or juice) themselves, and a beer brewer expecting to "design" a cider's starting gravity the way they'd design a beer's grain bill is in for a surprise: fresh-pressed juice typically arrives somewhere around 1.045-1.065 depending on the apple varieties and ripeness, and a home cider-maker's main lever over that starting point is blending juice from different sources or apple varieties, or adding a measured amount of sugar or honey to push it higher — not selecting and weighing a grain bill the way a beer recipe works. This is a genuinely different kind of recipe-formulation problem even though the downstream gravity arithmetic is identical.
Priming and carbonation work the same way, once you're past fermentation
The priming sugar calculator applies the identical physics to a bottle-conditioned cider as it does to a beer — residual CO2 correction, sugar-type ratios, the same roughly 3.5-volume bottle-safety ceiling all apply without modification. Where cider differs is the target itself: many ciders are carbonated to a lighter, more delicate level than a typical beer (some traditional ciders are barely carbonated at all, closer to still), while others — particularly a sparkling cider styled after champagne — push toward the top of what's safe in standard bottles or beyond it, needing genuinely champagne-rated glass the same way a hefeweizen or a Belgian golden strong does. There's no single "cider carbonation target" the way there's a rough consensus range for most beer style families; check what the specific cider tradition or recipe you're following actually calls for rather than assuming a beer-typical 2.4-volume target applies by default.
Back-sweetening and stabilizing: a genuinely cider-specific step
Many ciders are deliberately back-sweetened after fermentation — sugar or juice added back in to restore sweetness that fermentation removed, since a fully-fermented cider (as the attenuation figures above suggest) can finish extremely dry. This requires stabilizing the cider first — using potassium sorbate and/or potassium metabisulfite to prevent the yeast still present from simply refermenting the added sugar, which would just push the gravity back down and, in a sealed bottle, risk the same overcarbonation danger covered on what happens if I use too much priming sugar. This entire step — stabilize, then sweeten, then package still or force-carbonate rather than bottle-condition — has no direct equivalent in typical beer brewing, where back-sweetening a bottle-conditioned beer isn't standard practice at all.
Yeast choice is the other place cider genuinely differs
Cider is commonly fermented with wine or cider-specific yeast strains (Lalvin EC-1118, 71B, and similar) rather than typical beer ale strains, precisely because those strains are bred for the high attenuation and alcohol tolerance a dry cider or a stronger cider needs — a beer ale strain pitched into a cider must can genuinely underperform relative to what the fruit's fermentable sugar could otherwise produce. Check the yeast reference for published attenuation ranges before assuming your usual beer yeast will behave the same way on apple juice as it does on wort.