Grape Harvest Sugar to ABV Estimator
Estimate the potential alcohol by volume (ABV) of your wine from grape must sugar content measured in Brix, Baumé, or Specific Gravity. Uses industry-standard conversion formulas used by winemakers worldwide.
Typical range: 90–100%. Accounts for incomplete fermentation or residual sugar.
Formulas Used
1. Brix from Specific Gravity (Plato approximation):
Brix = 261.3 × (1 − 1 / SG)
2. Brix from Baumé:
Brix = Baumé × 1.8
3. Potential ABV from Brix (Boulton et al. winemaking formula):
Potential ABV (%) = [Brix ÷ (258.6 − Brix ÷ 1.0665)] × 76.08
4. Actual ABV with fermentation efficiency:
Actual ABV (%) = Potential ABV × (Efficiency ÷ 100)
5. Approximate sugar content:
Sugar (g/L) ≈ Brix × 10
6. Residual sugar:
Residual Sugar (g/L) ≈ Sugar (g/L) × (1 − Efficiency ÷ 100)
Assumptions & References
- The Boulton et al. formula is the industry-standard winemaking ABV estimation formula, more accurate than the simplified Brix × 0.55 rule, especially at higher sugar levels.
- The Brix-to-SG conversion uses the Plato approximation: Brix = 261.3 × (1 − 1/SG), accurate to within ±0.1 °Bx for typical must densities.
- The Baumé-to-Brix conversion (×1.8) is the standard used in Australian and European winemaking practice.
- Sugar content approximation of 10 g/L per °Brix is a standard winemaking rule of thumb; actual values vary slightly with grape variety and juice composition.
- Fermentation efficiency of 100% assumes complete fermentation of all sugars to ethanol and CO₂. Real-world values typically range from 90–100% depending on yeast strain, temperature, and nutrient availability.
- Residual sugar below 4 g/L is considered dry; 4–12 g/L is off-dry; above 45 g/L is sweet.
- Results are estimates only. Actual ABV should be confirmed by laboratory analysis (ebulliometer, distillation, or NIR spectroscopy) for commercial production.
- Reference: Boulton, R.B., Singleton, V.L., Bisson, L.F., & Kunkee, R.E. (1996). Principles and Practices of Winemaking. Springer.
- Reference: Iland, P., Bruer, N., Edwards, G., Weeks, S., & Wilkes, E. (2004). Chemical Analysis of Grapes and Wine. Patrick Iland Wine Promotions.