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TL;DR

• Nihonshu-do (日本酒度, sake meter value) measures specific gravity relative to water. Positive numbers skew dry; negative numbers skew sweet. The range most people encounter runs from about -5 (sweet) to +12 (very dry).
• Acidity (酸度) measures total acid concentration. Higher acidity = more structure, more tartness, more capacity to cut through fat.
• Amino acid level (アミノ酸度) measures free amino acids — the primary driver of umami and body.
• These numbers don’t operate in isolation. A high nihonshu-do sake with low acidity can taste sweeter than a negative-nihonshu-do sake with high acidity. The interaction is the whole game.
• Most premium sake labels print at least nihonshu-do and acidity. If you can read two numbers, you can make a better guess than most people buying blind.

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You are standing in the sake section of a Japanese grocery, which has seventeen bottles lined up between the mirin and the cooking wine. One of them has an informative English back label. The rest have Japanese text, a brewing date, and a small grid of numbers you cannot decode.

The numbers — on a standard brewers’ data panel — are nihonshu-do, acidity, and amino acid level. They are not a quality score. They are a fingerprint of what the sake will do to your palate. Understanding them takes about five minutes and changes how you buy for good.

Nihonshu-do: the dry-sweet axis

Nihonshu-do (日本酒度) is measured by a hydrometer: it compares the specific gravity of the sake to pure water. Water is 0 on the scale. Because sugar is denser than water, a sake with more residual sugar will have a negative reading — it is heavier than water. A sake with less residual sugar will have a positive reading — fermented further, lighter than water.

Nihonshu-do	General character
-5 or below	Noticeably sweet
-3 to 0	Slightly sweet to neutral
+1 to +4	Slightly dry, still approachable
+5 to +8	Dry — the Niigata style reference point
+9 and above	Very dry, sometimes austere

Niigata prefecture — where Hakkaisan and the Kubota brewery make their standard junmai — tends to land in the +5 to +8 range. Breweries aiming at a softer, sweeter profile for new drinkers typically stay negative. Neither is inherently better. They describe different drinking experiences.

One thing nihonshu-do does not tell you: how sweet the sake will actually taste. That depends heavily on acidity and amino acid level interacting with whatever your palate is carrying from the last thing you ate or drank.

Acidity: the structural axis

Acidity (酸度) is measured in milliliters of sodium hydroxide needed to neutralize 10 milliliters of sake — the standard titration approach. The higher the number, the more acid in the solution.

Most premium sake runs between 1.0 and 2.2. Standard ginjo and daiginjo tend to cluster at the lower end (1.0 to 1.4). Yamahai and kimoto styles — where the fermentation uses a naturally acidic lactic starter rather than a controlled commercial one — often run 1.6 and above.

What acidity does in the glass:

• Cuts sweetness perception. A sake with nihonshu-do of -2 and acidity of 1.8 will read drier than a sake with nihonshu-do of -2 and acidity of 1.0. The acid suppresses sweetness.
• Provides structure against fatty food. High-acid sake — a Tedorigawa Yamahai Junmai from Yoshida Sake Brewery in Hakusan, Ishikawa, for instance — performs with grilled proteins and oily preparations in the same way high-acid white wine does, without the tannin complication.
• Supports length. A sake with low acidity and moderate nihonshu-do often finishes flat. Acidity is what keeps the sake present on the palate after swallowing.

The practical shortcut: if you prefer sake with a crisp, clean finish and are choosing between two bottles, pick the one with higher acidity.

Amino acid level: the umami and body axis

Amino acid level (アミノ酸度) uses the same titration method as acidity and is printed alongside it on many labels. It measures the concentration of free amino acids — primarily glutamic acid — in the sake.

Typical range runs from 0.5 to 2.0. Standard daiginjo tends toward the lower end; yamahai and traditional kimoto styles run higher; aged sake (koshu) often runs higher still.

What free amino acids do:

• Umami: Glutamic acid is the free amino acid most directly associated with savory taste. A sake with amino acid level of 1.6 will reinforce the umami character of the food alongside it — aged cheese, shellfish, cured or fermented preparations.
• Body: Higher amino acid concentration gives a fuller, rounder mouthfeel.
• Aging potential: A higher amino acid level, combined with structured acidity, indicates more capacity to develop with time. Most sake is not improved by aging, but a well-acidic, high-amino sake is less likely to degrade quickly.

The flip side: very high amino acid level without corresponding acidity can make a sake taste heavy or muddy — the term Japanese brewers sometimes use is zatsuami, roughness. Balance between acidity and amino acid level is what the better breweries are calibrating.

The interaction effect — this is the counterintuitive part

The numbers only describe reality accurately in combination.

Consider two hypothetical sake:

Sake A: Nihonshu-do +6, acidity 1.0, amino acid level 0.8
Sake B: Nihonshu-do -1, acidity 1.7, amino acid level 1.3

Most buyers glancing at nihonshu-do would call Sake A dry and Sake B sweet. In the glass, the opposite is likely. The high acidity in Sake B suppresses sweetness and extends the finish. The low acidity in Sake A leaves residual sweetness from the grain more perceptible despite the positive meter value. Sake B, with its higher amino acid level and acid structure, will probably read drier, fuller, and more assertive.

This is why sake buyers who read only nihonshu-do — and many do — are often confused when their +8 sake tastes mild and their -1 sake tastes taut.

The practical working rules:

• To predict sweetness accurately: read nihonshu-do and acidity together. Low acidity amplifies apparent sweetness; high acidity suppresses it.
• To predict body: amino acid level is your primary signal.
• To predict food compatibility: acidity + amino acid level tells you more than nihonshu-do alone. High acidity → fatty, grilled, fermented food. High amino acid → umami-rich food.

Reading a label in practice

Most premium sake labels print the brewers’ specification (蔵元スペック) on the back or side panel. You are looking for a small data block that includes some or all of the following:

• 日本酒度 — nihonshu-do. A number, often with a + or - sign.
• 酸度 — acidity. A number with one decimal place, typically 1.x.
• アミノ酸度 — amino acid level. May be absent on ginjo labels; more common on junmai and traditional style labels.
• アルコール度数 — alcohol by volume. Typically 14-16%.
• 精米歩合 — rice polishing ratio. The grade-related number (50% = daiginjo threshold).

If you are buying from a US retailer, check the back label or the product page data. Tippsy Sake lists these specs on most product pages, which makes comparison shopping significantly more useful than guessing from a photograph of the front label.

The minimum useful read is nihonshu-do + acidity. If you can get amino acid level as well, you have a complete picture of what the sake will do — before you open it.

Where to explore labeled sake by style

Tippsy Sake is the most practical starting point for US buyers because most product pages include the numeric specs. You can use those numbers to test the framework — find two bottles with inverted nihonshu-do and acidity profiles, order both, and taste them side by side against the same food.

For UK buyers, The Whisky Exchange stocks a curated sake range with detailed tasting notes that often flag whether a sake runs dry, acidic, or full-bodied — useful shorthand for the same framework even when exact numeric specs are absent.

If you are in a city with a sake bar or dedicated sake sommelier, ask the sommelier to pour two sake with contrasting profiles and explain the numbers on the label. That conversation, with glass in hand, accomplishes in ten minutes what a table of abstractions takes longer to deliver.

The grade system — junmai, daiginjo, ginjo — tells you about production method. These three numbers tell you about the actual liquid. Both matter. But when you are standing at a shelf deciding, the numbers are faster.

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See also: Junmai vs Junmai Daiginjo vs Honjozo: A Guide to Sake Grades, Sake Pairing by Style, Not by Cuisine, Top 10 Sake Breweries Exporting to the US in 2026.