Brewing ABV and Attenuation Calculator
Estimate alcohol by volume and apparent attenuation from measured original and final specific gravity.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use the two specific-gravity readings on the same calibration basis and keep apparent attenuation separate from alcohol content.
Estimated ABV %=131.25(OG−FG); apparent attenuation %=100(OG−FG)/(OG−1)
Worked example
OG 1.050 and FG 1.010 give estimated ABV 5.25% and apparent attenuation 80%.
Assumptions and input details
Final gravity must not exceed original. Empirical common-strength beer estimate, not a laboratory alcohol determination. Temperature, dissolved gas and refractometer alcohol corrections must be handled before entry. Apparent attenuation is not true mass extract conversion.
References: Top-down Brew: alcohol calculation conventions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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