A mead ABV calculator built for meadmakers who want to see the full working — not just a number. Enter your original gravity (OG) before fermentation and your final gravity (FG) after, in either specific gravity (SG) or Brix/Plato, and the tool returns the ABV by two independent formulas, the apparent attenuation, the sweetness profile, and an estimated calorie count per serving. A bonus honey estimator panel lets you predict the starting gravity before you even pitch your yeast.
How it works
Gravity and fermentation
Honey is roughly 80% fermentable sugars dissolved in water. When you mix honey into water to make a must, the density of the liquid rises above 1.000 (the density of pure water). A hydrometer reads this as specific gravity (SG), or a refractometer converts it to °Brix (grams of sucrose per 100 g of solution). As yeast converts those sugars into ethanol and CO₂, the density falls. The difference between OG and FG is the signal from which ABV is calculated.
The two ABV formulas
Standard (simple) formula:
ABV = (OG − FG) × 131.25
This is accurate to within about 0.2% ABV for meads up to roughly 12%. It assumes a linear relationship between gravity drop and ethanol produced.
Advanced (Balling) formula:
ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)
This corrects for two effects the simple formula ignores: the contribution of the ethanol itself to the final density reading, and the changing ratio of ethanol yield per unit of sugar at higher gravities. It is the preferred figure for high-alcohol or sack meads (above ≈12% ABV).
Apparent attenuation
Attenuation (%) = (OG − FG) / (OG − 1) × 100
This tells you what fraction of the original fermentable sugars the yeast converted. A fully attenuated mead with a dry finish typically shows 90–98% attenuation. Residual sweetness comes from unfermented sugars, so a lower attenuation number means more sweetness.
Sweetness classification
The calculator labels the FG using the widely accepted meadmaking scale: below SG 1.005 is dry, 1.005–1.010 is off-dry, 1.010–1.020 is semi-sweet, 1.020–1.035 is sweet, and above 1.035 is dessert-sweet.
Worked example
A 10-litre traditional mead made with 3 kg of wildflower honey:
- Estimated OG from the honey estimator: SG 1.112 (≈ 26 °Brix)
- Final gravity after six weeks of fermentation: SG 1.008 (off-dry)
- ΔSG = 1.112 − 1.008 = 0.104
| Formula | Calculation | Result |
|---|---|---|
| Standard | 0.104 × 131.25 | 13.65% ABV |
| Advanced (Balling) | (76.08 × 0.104 / (1.775 − 1.112)) × (1.008 / 0.794) | 15.15% ABV |
| Attenuation | (1.112 − 1.008) / (1.112 − 1) × 100 | 92.9% |
At this gravity the mead sits in the off-dry category and carries roughly 230 kcal per 355 ml serving.
Quick reference: honey-to-OG conversion
| Honey (kg) per 10 L | Estimated OG | Typical ABV range |
|---|---|---|
| 1.0 kg | 1.037 | 4–5% |
| 1.5 kg | 1.055 | 6–8% |
| 2.0 kg | 1.073 | 9–10% |
| 2.5 kg | 1.092 | 11–12% |
| 3.0 kg | 1.110 | 13–14% |
| 3.5 kg | 1.128 | 15–16% |
Values assume 80% sugar yield and full dissolution. Actual OG can vary ±0.005 with honey variety, water temperature, and dissolution efficiency.
Tips for accurate readings
- Temperature-correct your hydrometer. Most are calibrated at 20 °C (68 °F). Warm must reads artificially low; cold must reads artificially high. Many hydrometers include a correction table, or you can add roughly +0.001 SG per 5 °C above calibration temperature.
- Use a hydrometer for FG, not a refractometer. Once ethanol is present a refractometer requires a correction formula (e.g., Novotný or Sean Terrill) because alcohol has a different refractive index to sugar.
- Two stable readings 48 hours apart confirm fermentation is complete before you record the FG. A single reading taken too early will over-report ABV.
- Degas the sample before reading — CO₂ bubbles cling to the hydrometer float and push it higher, leading to a falsely elevated FG.
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