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| OG | FG 1.005 | FG 1.010 | FG 1.015 | FG 1.020 | FG 1.025 |
|---|---|---|---|---|---|
| 1.040 (10.0 °P) | 4.6 | 4.0 | 3.3 | 2.6 | 2.0 |
| 1.045 (11.2 °P) | 5.3 | 4.6 | 4.0 | 3.3 | 2.7 |
| 1.050 (12.4 °P) | 6.0 | 5.3 | 4.7 | 4.0 | 3.3 |
| 1.055 (13.6 °P) | 6.7 | 6.0 | 5.3 | 4.7 | 4.0 |
| 1.060 (14.7 °P) | 7.3 | 6.7 | 6.0 | 5.3 | 4.7 |
| 1.065 (15.9 °P) | 8.0 | 7.4 | 6.7 | 6.0 | 5.4 |
| 1.070 (17.1 °P) | 8.7 | 8.0 | 7.4 | 6.7 | 6.0 |
| 1.075 (18.2 °P) | 9.4 | 8.7 | 8.1 | 7.4 | 6.7 |
| 1.080 (19.3 °P) | 10.1 | 9.4 | 8.8 | 8.1 | 7.4 |
| 1.085 (20.5 °P) | 10.8 | 10.1 | 9.5 | 8.8 | 8.1 |
| 1.090 (21.6 °P) | 11.5 | 10.8 | 10.2 | 9.5 | 8.8 |
| 1.095 (22.7 °P) | 12.2 | 11.5 | 10.9 | 10.2 | 9.5 |
| 1.100 (23.8 °P) | 12.9 | 12.2 | 11.6 | 10.9 | 10.2 |
Alcohol is computed with the Balling method, with OE and AE the original and apparent extract in degrees Plato:
RE = 0.1808 × OE + 0.8192 × AE
ABW = (OE − RE) / (2.0665 − 0.010665 × OE)
ABV = ABW × FG / 0.7907
The quick formula, ABV = (OG − FG) × 131.25, is shown for comparison. Plato and SG conversions use the ASBC polynomial. Hydrometer readings taken away from calibration temperature are corrected with the standard water density polynomial, reading × f(T) / f(Tcal), with f(T) = 1.00130346 − 0.000134722124 × T + 0.00000204052596 × T² − 0.00000000232820948 × T³ and T in °F. Refractometer final readings are corrected with Terrill’s cubic formula, original and final Brix divided by the wort correction factor:
FG = 1 − 0.0044993 × OB + 0.011774 × FB + 0.00027581 × OB² − 0.0012717 × FB² − 0.0000072800 × OB³ + 0.000063293 × FB³
Calories use the usual estimate, [(6.9 × ABW) + 4.0 × (RE − 0.1)] × FG × 3.55 per 12 oz, scaled to 33 cl. Label tolerances: Regulation (EU) 1169/2011, Annex XII, kept as is in UK law; 27 CFR 7.65(c) in the US.
The quick formula, (OG − FG) × 131.25, is a straight line fitted to average beers. Alcohol is lighter than water and the sugar left in the beer is heavier, so the line drifts as gravity rises. Balling’s method accounts for both. On a 1.050 beer finishing at 1.010 the gap is 0.07 percent; on a 1.090 beer finishing at 1.020 it is 0.3. Above 8 percent, use Balling.
In the EU and the UK, the stated figure may differ from the actual alcohol content by 0.5 percent vol for beers up to 5.5 percent, and by 1 percent vol above that (Regulation 1169/2011, Annex XII). In the US, the tolerance is 0.3 percentage points either way (27 CFR 7.65). Both apply to the alcohol content as measured, not as calculated from gravity.
Yes, with a correction. Alcohol bends light more than the sugar it replaced, so a raw final reading is too high. Terrill’s cubic formula uses the original and final Brix readings, both divided by the wort correction factor, and returns a final gravity within hydrometer accuracy for typical beers. On very strong or very sweet beers, confirm with a hydrometer.
Formula and data: Sean Terrill, Refractometer FG results, 2011.
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