Guides / Idle Games
Why Idle Games Use Huge Numbers: K, M, aa and e308 Explained
ONI Games · Published
What K, M, B, T, aa and 1.5e45 mean in idle games, why the numbers explode, why 1e308 is a magic limit, and how game code handles numbers bigger than a computer can hold, with our own bug story.
Idle games use huge numbers because everything in them grows exponentially: each upgrade multiplies income, so after a few hours you are in the millions and after a few weeks beyond anything with a name. To keep those numbers readable, games shorten them: K for thousand, M for million, B for billion, T for trillion, then letters such as aa, ab, ac, or scientific notation such as 1.5e45, which means 1.5 followed by 45 digits.
Cheat sheet: K = 10^3, M = 10^6, B = 10^9, T = 10^12, then each letter step is another 1,000x. In scientific notation, the number after the e counts the digits after the first one: 1e6 is a million, 1e12 a trillion.
The three common notations
| Value | Short scale | Letter notation | Scientific |
|---|---|---|---|
| 1,000 | 1K | 1K or 1a | 1e3 |
| 1,000,000 | 1M | 1M or 1b | 1e6 |
| 1,000,000,000 | 1B | 1B or 1c | 1e9 |
| 10^12 | 1T | 1T or 1d | 1e12 |
| 10^15 | 1Qa (quadrillion) | 1aa | 1e15 |
| 10^18 | 1Qi (quintillion) | 1ab | 1e18 |
| 10^33 | 1Dc (decillion) | 1ag | 1e33 |
Every game picks its own system, which is confusing but easy to decode once you know the rule: each step is a thousand times the last.
Real examples from our games
Even two games from the same studio can differ. In Idle AI Factory, numbers go K, M, B, T, and then two-letter groups start: aa for 10^15, ab for 10^18, ac for 10^21 and on through 120 suffixes. In Idle Ronin, letters start right away: 1a is a thousand, 1b a million, 1c a billion, all the way to z, then aa, bb, cc. The table has 1,743 suffixes, and if you ever go past the last one, the game prints "A Lot!". Idle Ronin also lets you switch to scientific notation in its settings, which many long-time players prefer.
Why the numbers explode
Costs and rewards in idle games grow by a percentage per step, which is exponential growth. In Idle Ronin, enemy health grows by 55 to 57% per stage early on. After 140 stages that compounding reaches about 10^28, a number with 29 digits. Our guide to how idle game progression works shows the curves.
Why 1e308 is a magic number
Most games store numbers as 64-bit floating point values, called doubles. The largest number a double can hold is about 1.8 x 10^308. Go past it and the computer gives you infinity. That limit is so famous among incremental players that Antimatter Dimensions made it part of the game: reaching Infinity, at about 1.8e308, is its first big goal.
A smaller format, the 32-bit float, runs out much earlier, at about 3.4 x 10^38. That matters, as we found out.
Our bug: when an enemy's health became infinite
Idle Ronin grew out of an older idle game, and in that code enemy health was calculated with 32-bit floats. Past stage 140, enemy health climbs into the 10^28 range, and from roughly stage 316 on the float overflowed to infinity. Later stages ended up with enemies that had no health at all, and around stage 1000 the calculation produced a NaN (not a number) that froze progress completely.
The fix was to calculate the whole curve with doubles, and to carry everything above stage 1000 in the game's own big-number type. It stores a normal number plus a separate count of extra zeros, so it can go far past the double limit. That is also why the game has a suffix table with 1,743 entries.
How games handle numbers beyond infinity
Browser incremental games hit the same wall, and their community built tools for it. The best known is break_infinity.js by Patashu, dedicated to Antimatter Dimensions' creator and "all the CPUs that struggled to run" the game. It stores the digits and the exponent as two separate numbers and reaches about 10^(9 x 10^15). Its successor, break_eternity.js, goes so far that it needs a tower of powers to describe its limit.
The trade-off is precision. Once numbers get this big, the game keeps only the first 15 or so digits. Nobody notices: when your income is 1.52e1204, the digits after the first few never matter.
How to read big numbers quickly
- Count the letters, not the digits. Each step (K to M, aa to ab) is 1,000 times bigger.
- In scientific notation, compare exponents. 3e45 is a thousand times more than 3e42.
- Switch notation if your game allows it. Scientific notation is easier to compare once numbers pass the named range.
- Think in multipliers. A x2 upgrade adds 0.3 to the exponent; a x10 upgrade adds 1.
FAQ
What comes after trillion in idle games?
Quadrillion (Qa), quintillion (Qi), sextillion, septillion and so on, or in letter notation aa, ab, ac. Each step is 1,000 times the previous one.
What does e mean in idle games?
Scientific notation: 1e6 means 1 followed by 6 zeros, a million. 2.5e20 means 2.5 followed by 20 digits.
What does aa mean in idle games?
In most games with letter notation, aa is the first step after trillion, 10^15. Some games, like Idle Ronin, start letters earlier, so check the game's own scale.
Why do idle games stop at 1e308?
Because a standard 64-bit number cannot go higher. Games that go further use their own number types.
Sources
- ONI Games game code: Idle Ronin (double_evrac.cs, PlayerDatabase.CalculateEnemyHP) and Idle AI Factory (NiceCurrencyFormat.cs), September 2026.
- break_infinity.js and break_eternity.js, Patashu, GitHub.
