Homebrew Alcohol by Volume (ABV) & Hydrometer Temperature Calculator
Reading a hydrometer while wort or beer is warmer or cooler than the instrument's calibration temperature introduces real error into your gravity numbers, which then skews your ABV calculation. This tool applies the standard polynomial temperature correction before computing true ABV, attenuation and rough calories per bottle.
Corrected for a 68°F sample against a 60°F calibrated hydrometer, this brew finishes at 5.91% ABV with 80.7% apparent attenuation.
| Measure | Value |
|---|---|
| Raw OG entered | 1.0550 |
| Raw FG entered | 1.0100 |
| Sample temp | 68.0°F |
| Calibration temp | 60°F |
| Corrected OG | 1.0558 |
| Corrected FG | 1.0108 |
| ABV % | 5.91% |
| Calories / 12oz bottle (est.) | 45,746 kcal |
- 1.
Correction(T) = (1.00130346 − 0.000134722121·T + 0.00000204052596·T² − 0.00000000232820948·T³) / Correction(Tcal) - 2.
TrueSG = RawSG × Correction(T) - 3.
ABV% = (TrueOG − TrueFG) × 131.25 - 4.
Attenuation% = ((TrueOG − TrueFG) / (TrueOG − 1.0)) × 100
How to Use This Calculator
1. Enter your details
Use the labelled fields and units that match your situation.
2. Calculate instantly
The result, visual comparison, and working update as values change.
3. Review your result
Check assumptions, then copy, print, or share the calculation.
Formula & step-by-step maths
- T
- Sample temperature in °F
- Tcal
- Hydrometer calibration temperature
Why temperature correction matters
Glass hydrometers are calibrated at a specific temperature, usually 60°F or 68°F. Liquid expands when warm, making the hydrometer float higher and read a falsely low gravity. Correcting for temperature before subtracting FG from OG prevents ABV from being over- or under-stated by several tenths of a percent.
Reading the ABV formula
The simplified formula ABV% = (OG − FG) × 131.25 is accurate for most homebrew gravity ranges and is the standard used by most homebrew software, though high-gravity beers benefit from more complex formulas for extra precision.
What attenuation tells you
Apparent attenuation shows what percentage of the extract in your wort was fermented into alcohol and CO2. Most ale yeasts land between 72-82%; a reading well outside that range can signal a stuck fermentation or an unusually attenuative yeast strain.
Using calorie estimates responsibly
The calorie estimate is a widely used approximation based on final gravity and alcohol content, not a lab measurement — treat it as a rough guide for homebrew nutrition labels rather than an exact figure.
Typical style ABV & attenuation ranges
| Style | Typical OG | Typical ABV |
|---|---|---|
| Light Lager | 1.040-1.050 | 4.2-5.3% |
| American Pale Ale | 1.045-1.056 | 4.5-6.2% |
| IPA | 1.056-1.070 | 5.5-7.5% |
| Stout | 1.050-1.075 | 4.0-7.5% |
| Belgian Tripel | 1.075-1.085 | 7.5-9.5% |
| Barleywine | 1.080-1.120 | 8-12% |
Frequently Asked Questions
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: original gravity (og) 0.98, hydrometer calibration temp "60°F"
On the lower / more conservative end. Corrected for a 68°F sample against a 60°F calibrated hydrometer, this brew finishes at -3.94% ABV with 156.1% apparent attenuation.
Example 2: original gravity (og) 1.06, hydrometer calibration temp "60°F"
A typical middle-of-the-road setup. Corrected for a 68°F sample against a 60°F calibrated hydrometer, this brew finishes at 6.57% ABV with 82.3% apparent attenuation.
Example 3: original gravity (og) 1.37, hydrometer calibration temp "68°F"
On the higher / more demanding end. Corrected for a 68°F sample against a 68°F calibrated hydrometer, this brew finishes at 47.25% ABV with 97.3% apparent attenuation.
Quick answers about the Homebrew ABV & Hydrometer
What exactly does the Homebrew ABV & Hydrometer work out?
Reading a hydrometer while wort or beer is warmer or cooler than the instrument's calibration temperature introduces real error into your gravity numbers, which then skews your ABV calculation. You enter original Gravity (OG), final Gravity (FG), sample Temperature and hydrometer Calibration Temp and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 4 fields: original Gravity (OG), final Gravity (FG), sample Temperature and hydrometer Calibration Temp. Nothing else is needed and nothing is stored.
How is it calculated — why temperature correction matters?
Glass hydrometers are calibrated at a specific temperature, usually 60°F or 68°F. The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for homebrew ABV & Hydrometer?
The simplified formula ABV% = (OG − FG) × 131. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Typical style ABV & attenuation ranges" table on this page tell me?
It is the reference range this tool works against — 6 rows from "Light Lager" (1.040-1.050) up to "Barleywine" (1.080-1.120). Use it to sanity-check whether the number you just calculated sits where you expected it to.
Which hydrometer Calibration Temp should I pick?
The dropdown offers 2 choices — 60°F and 68°F. Pick the one that matches your real situation rather than the one you would like to be true; hydrometer Calibration Temp usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Do I have to press a button or reload the page to see the result?
No. Homebrew ABV & Hydrometer runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Homebrew ABV & Hydrometer leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
No — if the sample temperature matches the calibration temperature the correction factor is 1. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
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