Big Number Notation Explained: K, M, B, T, aa, ab, and Beyond

You just logged into your idle game, watched the offline-earnings counter tick past something like 1.23aa, and now you're squinting at the screen wondering whether that's a small number, a medium number, or a number that just bought you the rest of the tech tree. Most idle games use one of three notation systems: short-scale English (K, M, B, T, Quadrillion…), compact short-scale abbreviations (K, M, B, T, Qa, Qi, Sx…), or alphabetic suffixes (K, M, B, T, aa, ab, ac…). The suffix you're looking at tells you which system the game picked. Once you know the system, decoding the number is a five-second exercise. The rest of this article makes that decode automatic, then explains why three different games can show the same quantity three different ways.

Decode my number right now

Why idle games need their own notation

Scientific notation (1.5e30) is mathematically perfect and emotionally flat. Every order of magnitude looks identical on screen. 1e29 and 1e30 differ by a factor of ten, which is the entire purpose of the next prestige tier, and your brain registers them as "two numbers that look the same." Idle games run on watching numbers grow, and a number that doesn't look like it grew is a broken reward.

Suffix conventions exist to fix this. K feels small. T feels respectable. aa feels like you broke containment. Each new suffix is a visual milestone: the player crosses a threshold, the units flip, the upgrade tree responds. Designers reach for word-based or letter-based systems because they scan at a glance and read as emotionally larger the way 3.4e21 doesn't. The price is that English runs out of common words around trillion, and what happens after that varies game to game.

Table 1: Short-scale notation (K, M, B, T…)

This is the standard English system used in the United States, modern UK, and most idle games shipped in English. Cookie Clicker uses full short-scale names (the in-game "Short numbers" option toggles between full digit displays and these words). AdVenture Capitalist uses the same convention, extending through Centillion (10^303) before the game hits its JavaScript floating-point ceiling and displays $In.fin.

Construction rule: the Latin prefix tells you the position. Quattuorvigintillion = "four-and-twentieth illion" = 10^((24×3)+3) = 10^75. AdVenture Capitalist players hit Centillion territory after a few weeks of moderate prestige play. The value $1.798e308 is JavaScript's Number.MAX_VALUE, where AdC literally cannot represent a larger number without a math library.

Table 2: Compact short-scale abbreviations (Qa, Qi, Sx…)

This is the messy middle. Games that want short-scale logic but not three-syllable Latin words abbreviate everything past trillion to two or three letters. Antimatter Dimensions' "Standard" notation uses this convention through Nonillion before flipping to mixed scientific. Many Roblox simulator games and mobile idle titles use the same two-letter codes.

Case-sensitivity warning. Conventions disagree. The dominant pattern, used in Antimatter Dimensions, most Roblox templates, and BreakInfinity-derived games, has a capital first letter and lowercase second: Qa, Qi, Sx, Sp, Oc, No, Dc. Some games invert it (using qa for quadrillion and Qa for quintillion to disambiguate), and a handful of community-fan-port games use all-lowercase qa, qi, sx. If a game uses both Qa and Qi, you're in the dominant convention. If the same game uses qa and Qa as distinct suffixes, lowercase is the smaller order; this scheme is rare and usually a porting artifact. Quintillion is also unstable: some codebases abbreviate it Qi, others Qt. Both mean 10^18.

Table 3: Alphabetic suffix notation (aa, ab, ac…)

Alphabetic suffixes exist because English ran out of comfortable words and designers got tired of typing Quattuorvigintillion. There are two alphabetic systems in active use, and they disagree about where aa starts. This is the single biggest source of confusion in the genre.

System A: the mobile/Egg Inc convention. Used by Egg Inc, Idle Miner Tycoon, Gold and Goblins, and most mobile idle games. Real English names through trillion, then alphabetic pairs start at quadrillion.

System B: the Antimatter Dimensions "Letters" convention. Single letters start at 10^3, doubled letters start at 10^81. AD popularized this approach but it predates the game in several earlier incremental titles.

Same suffix, different exponents. aa in Egg Inc is 10^15. aa in Antimatter Dimensions' Letters notation is 10^81. If a game uses K/M/B/T anywhere in its UI, it's almost always System A. If it never uses K/M/B/T and the lowercase letters start from a, it's System B. After zz in either system, the convention continues to aaa, then aab, aac… through zzz, then aaaa. The scheme is base-26 in lowercase letters with the leftmost letter as the most significant digit.

The cultural fork: same number, three games

Take 10^50: large enough to sit inside every modern idle game's progression, small enough that none of them have run out of room for it. Same antimatter, three displays:

• Cookie Clicker: 1.0 quindecillion (full short-scale English).
• Antimatter Dimensions, default Scientific notation: 1.00e50 (mantissa and exponent separated by e).
• AdVenture Capitalist: 1.00 Quindecillion (also full short-scale English).
• Antimatter Dimensions, Standard notation toggled on: 1.00 QiDc (compact two-letter codes for the same word).
• A mobile idle clone using aa-notation: 1.00 mh (System A: 10^15 = aa, so 10^50 lands on mh, the twelfth pair, sixth column).

Three games, three philosophies. Each one tells you who its game is for.

Antimatter Dimensions defaults to Scientific notation because its players are post-cookie, post-AdC, post-feeling. They are there for the math. The game ships with 24 notations on web (Scientific, Engineering, Letters, Standard, Mixed Scientific, Mixed Engineering, Logarithm, Brackets, Infinity, Roman, Dots, Hex, Imperial, Clock, Prime, Bar, Zalgo, Shi, Blind, Blobs, Emoji, and a few more) and lets the player pick. The other 23 are mostly jokes or roleplay. The default tells you the truth: AD's audience wants log-scale legibility. They want to know if they jumped two orders of magnitude on the last prestige. 1.00e50 → 1.00e60 reads that instantly. Quindecillion → Octodecillion doesn't. AD could have used alphabetic suffixes and chose not to, which tells you something about who the game is for.

Cookie Clicker uses long short-scale words because Orteil wanted readability over compression. The game's "Short numbers" toggle is opt-in; the default display is the literal cookie count, which keeps the early game grounded in real numbers. When word-mode kicks in, Cookie Clicker says Quadrillion, not Qa. Orteil's audience is browser-tab idlers, not spreadsheet players. The full word does emotional work an abbreviation can't.

AdVenture Capitalist sits in the middle. The game is built around an upgrade loop where the next multiplier is always 10x or 100x larger than the last; players need to scan ten lines of upgrade costs and pick the best buy in under a second. AdC stuck with full English short-scale words for the same reason Cookie Clicker did, but pays for it later, when Octononagintillion (the game actually displays the misspelling Onctononagintillion) starts showing up. The choice to use long words at every tier is what makes endgame AdC charmingly absurd.

The aa/ab/ac mobile clones (Egg Inc, Idle Miner Tycoon, Gold and Goblins) optimized for the smallest possible screen footprint. Phone screens can't fit Quattuorquadragintillion. They can fit 1.2 ph. Every notation system here is a tradeoff between three competing pressures: precision, emotional payoff, and pixel width. Each game picked a different point in that triangle.

Beyond aa: when even alphabetic suffixes run out

The two-letter alphabetic system gives you 676 distinct suffixes, enough for 10^(15 + 3×675) = 10^2040 in System A. Past that, games switch to triple letters (aaa, aab…) or give up and fall back to scientific notation. The most-used large-number library in idle games is break_infinity.js, used by Antimatter Dimensions and dozens of derivatives; it caps out at roughly 1e9e15, meaning 10 raised to the nine-quadrillionth power. Past that, games migrate to break_eternity.js or OmegaNum.js, which represent numbers using stacked scientific notation: e1e100 means 10^(10^100), and ee1e100 means 10^(10^(10^100)). After enough stacked e's, OmegaNum switches to hyperscientific using Bowers's curly-brace operator: 10{2}3 is tetration, 10{3}3 is pentation, and on into Knuth up-arrow territory.

Antimatter Dimensions handles the upper limit with a UI trick. Hit a value past the game's internal cap and the display flips to the literal word Infinite, used as a fallback rather than a completion state. The game's "Infinity" notation does this on purpose: it displays 0.0165∞, a logarithmic ratio of how close you are to JavaScript's 1.798e308.

How to read scientific notation in idle games

If you landed here because your screen says 1.23e+45 and you don't speak math, here's the decoder. The e is shorthand for "times ten to the power of." So 1.23e+45 = 1.23 × 10^45 = a 1 followed by 45 zeros, then shifted by the 1.23 multiplier. To compare two e-notation numbers fast, look at the exponent first. 1.0e60 is always bigger than 9.9e59, because the exponent (60) is larger than (59), regardless of the mantissa. Only when exponents match does the mantissa matter. 3.4e80 beats 1.1e80, and 1.1e80 beats 9.9e79. That single trick decodes 95% of scientific-notation displays in 95% of idle games.

FAQ

What does aa mean in idle games? In most mobile idle games (Egg Inc, Idle Miner Tycoon, Gold and Goblins), aa = 10^15 = one quadrillion. The sequence continues: ab = 10^18 (quintillion), ac = 10^21 (sextillion), and so on. In Antimatter Dimensions' "Letters" notation, aa instead means 10^81, because that system starts the alphabet at 10^3 and only doubles letters after z.

What comes after trillion in Cookie Clicker? Quadrillion (10^15), then quintillion (10^18), sextillion (10^21), septillion (10^24), octillion (10^27), nonillion (10^30), decillion (10^33), and onward through the full Latin short-scale series. Cookie Clicker's "Short numbers" option in the Options menu controls whether these names display.

Why don't idle games just use scientific notation? Scientific notation is precise but emotionally flat. 1e29 and 1e30 look almost identical, even though one is ten times the other. Suffix systems give each new threshold a visual identity, which is the entire reward loop of the genre. Math-forward games like Antimatter Dimensions default to scientific anyway because their audience prefers it.

What does 1e30 mean in an idle game? It means 1 × 10^30, a 1 followed by thirty zeros, which is one nonillion in short scale. In suffix-style games, the same value displays as 1.00 No (compact), 1.00 Nonillion (Cookie Clicker / AdC), or 1.00 af (Egg Inc-style aa-notation).

What's the biggest number you can reach in an idle game? JavaScript's native limit is 1.798e308, which is where AdVenture Capitalist halts. Games using break_infinity.js (Antimatter Dimensions and similar) reach roughly 1e(9×10^15). Games using OmegaNum.js or break_eternity.js extend into tetration and beyond, with no practical ceiling short of the game's own design.