Homebrew ABV Calculator
The homebrew ABV calculator tells you the alcohol by volume of your beer, wine, mead, or cider from two hydrometer readings — the original gravity (OG) taken before fermentation and the final gravity (FG) taken after. Type both numbers and it instantly returns the ABV percentage plus the apparent attenuation, with a toggle between the standard formula and an alternate formula for stronger brews. It runs entirely in your browser — no signup, no app to install, nothing uploaded.
Enter your original gravity (OG) and final gravity (FG) in the two fields, and the ABV percentage plus apparent attenuation update instantly above. Use the Standard formula for ordinary beers, or Alternate for high-gravity brews, wine, and mead.
Got your OG and FG readings? Get your ABV in one look.
Use the free ABV Calculator →How to Use the Homebrew ABV Calculator
There are just two readings to enter, and the result updates the moment you type — no submit button:
- Open capsuletools.app/abv-calculator/
- Original Gravity (OG) — type the hydrometer reading you took before pitching yeast (for example 1.050)
- Final Gravity (FG) — type the reading you took once fermentation finished (for example 1.010)
- Formula — leave it on Standard for ordinary beers, or switch to Alternate for strong brews, wine, and mead
The big number is your alcohol by volume; below it sits the apparent attenuation — how far the brew fermented out. If the final gravity isn't lower than the original, the tool flags it, since a finished ferment always drops in gravity.
Final Gravity = 1.010
Alcohol by volume = 5.25%
Apparent attenuation = 80%
How ABV Is Calculated from Gravity
Sugar is denser than water, and alcohol is lighter than water. Before fermentation your wort is packed with sugar, so it reads high on a hydrometer — that's the OG. As yeast converts sugar to alcohol and CO₂, the liquid gets less dense and the reading falls to the FG. The size of that drop is proportional to the alcohol produced, which is why ABV comes straight from OG and FG. The standard homebrew formula is:
So an OG of 1.050 finishing at 1.010 gives (1.050 − 1.010) × 131.25 = 5.25% ABV. No temperature correction is applied here — take your readings at, or corrected to, your hydrometer's calibration temperature (usually 60 °F / 20 °C) for the most accurate result.
Standard vs. Alternate ABV Formula — Which to Use
The standard formula above is a straight-line approximation. It's accurate for most beers up to about 1.070 OG, but it reads slightly high on strong worts because the link between gravity drop and alcohol isn't perfectly linear at higher strengths. The alternate formula corrects for that curve:
Use Standard for everyday-strength beer and cider, and switch to Alternate for high-gravity beers, barleywines, wine, and mead. The difference is small at low strength and grows as the brew gets stronger — this calculator lets you flip between them so you can see it for yourself.
Understanding Apparent Attenuation
Apparent attenuation is how far your brew fermented out, expressed as the percentage of the original gravity points the yeast consumed:
For OG 1.050 and FG 1.010 that's (0.040 ÷ 0.050) × 100 = 80%. Most ale yeasts finish around 72–80%, so this is the number you compare against your yeast strain's rated range to judge whether the ferment is done or stalled. It's called "apparent" because a hydrometer also senses the alcohol's low density, so the figure runs a touch above true attenuation — but 80% is the standard value brewers quote.
ABV Calculator for Beer, Wine, Mead & Cider
The same OG/FG method works across every homebrew ferment — only the typical gravity ranges differ:
| Ferment | Typical OG | Best formula |
|---|---|---|
| Beer | 1.040–1.060 | Standard |
| Cider | 1.045–1.055 | Standard |
| Strong / imperial beer | 1.070–1.100 | Alternate |
| Wine | 1.070–1.100 | Alternate |
| Mead | 1.090–1.140 | Alternate |
For wine and mead the alternate formula is the safer choice because they start high and often finish dry — exactly where the simple formula drifts. Take your OG before pitching and your FG once the brew has stabilised for several days at the same reading, then enter both here.
Frequently asked questions
How is ABV calculated from gravity readings?
ABV is worked out from the drop in gravity between your original gravity (OG, before fermentation) and final gravity (FG, after). The standard homebrew formula is ABV = (OG − FG) × 131.25. For example, an OG of 1.050 and an FG of 1.010 gives (1.050 − 1.010) × 131.25 = 5.25% ABV. The gravity fell because the yeast turned dense sugar into lighter alcohol, so the size of that drop tells you how much alcohol was produced.
What's the difference between original gravity (OG) and final gravity (FG)?
Original gravity (OG) is the hydrometer reading of your wort or must before fermentation, when it is full of sugar and denser than water. Final gravity (FG) is the reading after fermentation, once the yeast has converted much of that sugar to alcohol and the liquid is less dense. FG is always lower than OG in a finished brew, and the gap between the two is what the ABV calculation is based on.
Should I use the standard or alternate ABV formula?
Use the standard formula, ABV = (OG − FG) × 131.25, for ordinary-strength beers up to about 1.070 OG — it's simple and accurate in that range. Switch to the alternate formula for high-gravity brews, strong ales, wine, and mead, where the simple formula reads a little high. The alternate formula corrects for the fact that the relationship between gravity drop and alcohol is not perfectly linear at higher strengths. This calculator lets you toggle between the two.
What is apparent attenuation and how do I calculate it?
Apparent attenuation is the percentage of the original gravity points that the yeast fermented away — a measure of how far the brew fermented out. It's calculated as (OG − FG) ÷ (OG − 1) × 100. For OG 1.050 and FG 1.010 that's (0.040 ÷ 0.050) × 100 = 80%. It's called "apparent" because a hydrometer also senses the alcohol's low density, so the figure slightly overstates true attenuation, but 80% is the number brewers quote and compare against a yeast's rated range.
How do I measure ABV in mead?
Measure the gravity of your must with a hydrometer before pitching yeast (the OG), then again once fermentation is complete (the FG), and enter both here. Because mead starts at a high gravity and can finish quite dry, choose the alternate formula for a more accurate reading. A mead going from OG 1.100 to FG 1.000 works out to roughly 13% ABV on the alternate formula.
How do I measure the alcohol content of cider?
Cider ABV is measured the same way as beer: take a hydrometer reading of the fresh juice before fermentation for your OG, then a final reading once it has fermented out for your FG, and enter both. Fresh apple juice is often around 1.045–1.055 and dry cider typically finishes near 1.000, so a common result is about 6–7% ABV. The standard formula is fine for most ciders.
Related tools
Fabric Gathering Calculator
Test swatch → flat fabric to cut for gathers & ruffles
How Fabric Gathering Calculator works
Break-Even Calculator
Fixed & variable costs + price → break-even point + chart
How Break-Even Calculator works
Compressed Insulation Calculator
Effective R-value of batt insulation squeezed into a cavity
How Compressed Insulation Calculator works
