Gravity Reading Log: The Ultimate Guide to Tracking Mead Fermentation Progress

Knowing exactly where your mead stands in fermentation—hour by hour, gravity point by gravity point—is the single most reliable way to prevent a stuck batch, time your nutrient additions correctly, and brew consistent mead every time. A well-kept gravity reading log turns a guessing game into a data-driven process, and the numbers are clear: a standard traditional mead runs from an OG of 1.080–1.120 down to a FG of 0.990–1.010 for dry styles, with the critical 1/3 sugar break sitting roughly one-third of the way through that drop ^[1].

• OG tells you what you started with: Most standard meads begin in the 1.080–1.120 range; session-strength hydromels start lower (1.035–1.080); big sack meads can reach 1.120–1.170 ^[3].
• The 1/3 sugar break is your most important checkpoint: It marks the gravity at which yeast are most stressed and most in need of nutrients ^[1].
• FG determines sweetness: Dry meads finish at 0.990–1.010; semi-sweet at 1.010–1.025; sweet at 1.025 and above ^[3].
• Refractometers lie after fermentation starts: Alcohol distorts light refraction, making a hydrometer the only reliable mid-fermentation tool unless you apply a correction formula ^[4].
• Early stall detection saves batches: Catching a plateau within 24–48 hours gives you time to add nutrients, adjust temperature, or re-pitch before irreversible off-flavors develop ^[6].
• Logging is not optional—it's your troubleshooting record: Without a written gravity timeline, diagnosing a stall is nearly impossible.

TL;DR: Log your gravity at every key milestone, use a hydrometer once alcohol is present, and you'll have everything you need to catch stalls early and produce mead that finishes exactly where you intended.

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Understanding the Gravity Milestones That Matter

Fermentation is not a straight line. Honey must behaves very differently from a simple sugar wash, and the first step in tracking it effectively is knowing which gravity readings actually carry diagnostic weight.

Original Gravity: Setting the Baseline

Your original gravity (OG) reading—taken immediately before or just after pitching yeast—is the anchor for every calculation that follows. Without an accurate OG, you cannot compute your 1/3 break, your target ABV, or whether your fermentation is progressing at a normal rate ^[3].

Mead styles fall into three broad OG brackets ^[3]:

• Hydromel (session mead): OG 1.035–1.080, ABV target 3.5–7.5%
• Standard traditional: OG 1.080–1.120, ABV target 7.5–14.0%
• Sack mead (high gravity): OG 1.120–1.170, ABV target 14.0–18.0%

For a standard 5-gallon batch targeting OG 1.090 with a dry finish around 1.000, ABV is estimated using the formula (OG − FG) × 131.25, which in this case yields roughly 11.8% ^[8]. Record this number in your log the moment must is in the fermenter—before any temperature or honey additions are forgotten.

The 1/3 Sugar Break: Your Most Critical Checkpoint

The 1/3 sugar break is the gravity at which yeast transition from their most vigorous growth phase into a more alcohol-stressed state. This is the point where nutrient deficiency, osmotic stress, and temperature swings are most likely to trigger a stall—and it's the checkpoint most beginner meadmakers miss entirely because they're not logging readings frequently enough.

The calculation is straightforward ^[1]: subtract your target FG from your OG, divide by three, and subtract that result from your OG. For a must with OG 1.090 and target FG 1.000, the 1/3 break falls at approximately 1.060 ^[1].

Nutrient protocols like TOSNA time additions to this exact moment. A typical schedule calls for additions at pitching, at 48 hours, at 96 hours, and again when you hit the 1/3 break ^[2]. If you're not logging gravity readings frequently enough to catch this window, you're flying blind through the period when your yeast need you most. For a deeper look at nutrient timing strategies, see our guide to TOSNA vs. Fermaid-O vs. Go-Ferm.

Final Gravity and Sweetness Targets

Final gravity (FG) tells you both how fermentation completed and whether your mead hit the sweetness profile you intended. Homebrewers often fixate on bubbling as a proxy for fermentation health—but CO₂ activity can stop for many reasons that have nothing to do with whether your mead is actually done.

Sweetness categories by FG ^[3]:

• Dry: 0.990–1.010 (most or all sugars consumed)
• Semi-sweet: 1.010–1.025
• Sweet: 1.025 and above

A dry mead typically finishes at or just below 1.000–1.005, meaning the yeast have consumed the vast majority of fermentable sugars ^[8]. Confirm true completion by taking readings on three consecutive days; if the gravity is stable across all three, fermentation is genuinely finished—not just paused.

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Hydrometer vs. Refractometer: Which Tool to Use and When

This is one of the most common points of confusion in home meadmaking, and getting it wrong will cost you accurate data at exactly the moments you need it most.

Why the Refractometer Fails Mid-Fermentation

A refractometer measures how much a liquid bends light (its refractive index), then translates that into a Brix or specific gravity reading. Before fermentation, when must contains only water, honey sugars, and nutrients, a refractometer gives a fast and reasonably accurate OG reading from just a drop or two of liquid—making it a popular tool for pre-pitch measurement ^[5].

The problem emerges once yeast begin converting sugar to alcohol. Alcohol refracts light differently than sugar, and the refractometer's scale cannot distinguish between them ^[4]. Once fermentation has started, a raw refractometer reading will report a gravity significantly higher than the actual value—meaning you may believe you're stuck at 1.030 when you're actually at 1.012 ^[4]. This false reading can lead to unnecessary and harmful interventions.

"The hydrometer reading would be the correct reading if fermentation has started." — HomeBrewTalk Community, Hydrometer vs. Refractometer Thread ^[4]

Correction Formulas: Using a Refractometer Accurately Mid-Batch

If you prefer the convenience of a refractometer during primary fermentation, you can obtain usable data—but only by applying a correction formula. The Terrill correction (also called the Sean Terrill cubic correction) is widely regarded as the most accurate option available ^[7]. It requires both your original Brix reading and your current Brix reading and outputs a corrected specific gravity.

The linear version of the Terrill correction is ^[7]:

FG_SG = 1 – 0.00085683 × OG_Brix + 0.0034941 × FG_Brix

Practically speaking, this means your refractometer is a pre-pitch convenience tool, not a mid-fermentation measurement device, unless you are consistently running correction calculations. Most meadmakers find it simpler and more reliable to use a calibrated hydrometer for all readings after pitch.

For best results ^[7]:

• Calibrate your refractometer with distilled water before every session.
• Take samples at the same temperature (ideally 20 °C / 68 °F).
• Log both the raw Brix reading and the corrected SG value so you can audit your data later.

Building Your Measurement Toolkit

Whichever tool you choose, consistency matters more than precision. A reading taken the same way, with the same instrument, at the same temperature every 48 hours gives you a trend line—and trend lines are what detect stalls.

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How to Build a Gravity Reading Log That Catches Stalls

Logging gravity is only valuable if your log is structured to surface problems early. Here's how to design a gravity reading log that works as a real diagnostic tool.

What to Record at Every Reading

A bare minimum gravity entry should include:

1. Date and time of the reading
2. Gravity value (SG, corrected if using refractometer)
3. Temperature of the must at time of reading
4. Observations: aroma, color, airlock activity, visible lees
5. Interventions made: nutrient additions, temperature changes, degassing

Many meadmakers also note the point drop since last reading (e.g., "dropped 0.008 in 48 h"). This derived metric is the single fastest way to spot a stall—if your point drop has slowed from 0.010 per 48 hours to 0.001, you have a developing problem, not an incidental fluctuation ^[6].

Logging Frequency by Fermentation Stage

Readings taken less frequently than every 48 hours during active fermentation can allow a stall to develop undetected for four or more days—long enough for off-flavors from stressed yeast to begin accumulating ^[6].

Recognizing Stall Patterns in Your Data

A stuck fermentation is defined not by the absence of bubbling, but by the absence of gravity change over 48–72 hours at a gravity above the yeast's expected FG. Common stall patterns to watch for in your log:

• Early stall (above 1/3 break): Often caused by poor yeast hydration, osmotic stress, or nitrogen deficiency. Intervention: nutrient addition, gentle warming ^[6].
• Mid-fermentation plateau (between 1/3 and 2/3 break): Frequently tied to temperature drop or CO₂ toxicity. Intervention: degassing, temperature stabilization ^[6].
• Late stall (below 2/3 break, above expected FG): Often caused by alcohol toxicity or nutrient exhaustion. Intervention: re-pitching with an acclimated yeast starter. See our guide to re-pitching yeast in a stuck mead.

"A slow or stuck mead fermentation is a simple issue with a simple fix—but you have to catch it early." — Homebrew Academy, Restarting Stuck Mead Fermentation ^[6]

If you've logged diligently and your gravity is genuinely stalled, don't panic. The same data that confirms a stall also tells you which kind of stall you're dealing with—and that context determines the right fix. Our companion article on why mead stops fermenting walks through the seven most common causes in detail.

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Practical Gravity Log Templates and What the Numbers Mean

Knowing the theory is half the battle. Here's how to translate your logged numbers into concrete decisions.

Sample Gravity Timeline for a Standard Mead (OG 1.090)

Based on established fermentation benchmarks ^[1][2][3], a healthy standard mead with OG 1.090 and FG target 1.000 should produce a log that looks roughly like this:

Any reading that falls significantly outside the expected range—especially a gravity that barely changes between Day 4 and Day 6 during what should be peak fermentation—is a red flag worth acting on immediately.

Calculating Your Own 1/3 Break

You don't need a calculator to find your 1/3 break. The formula is ^[1][2]:

1/3 Break = OG − [(OG − Target FG) ÷ 3]

Examples:

• OG 1.080, FG target 1.000 → 1/3 break at 1.053
• OG 1.100, FG target 1.010 → 1/3 break at 1.070
• OG 1.120, FG target 1.000 → 1/3 break at 1.080

Log these target values before fermentation starts so you know exactly what gravity to watch for—and so that when your reading hits that number, your nutrient dose is already prepared.

From Manual Log to Smart Detection

A paper log works, but it has a fundamental limitation: it cannot alert you when a trend line flattens. You have to look at it and do the arithmetic yourself. This is where MeadStall changes the workflow entirely. By entering your gravity readings as you take them, MeadStall automatically plots your fermentation curve, calculates your 1/3 and 2/3 breaks in real time, and flags plateau patterns before they become full stalls—then surfaces the specific troubleshooting step appropriate to your fermentation stage and the inputs you've logged. Whether you're managing your first hydromel or a complex sack mead, the right data at the right time is the difference between a thriving batch and a bottle of expensive vinegar.