Guides / Idle Games
Idle Game Calculator: Upgrade Costs, Time to Buy and When to Prestige
ONI Games · Published
Five free calculators for any idle game: what the next levels cost, how long until you can buy them, which upgrade pays for itself first, how much faster a prestige makes you, and what 1e15 or 1aa means. With the math behind each one.
Every idle game runs on the same few formulas: each level costs a fixed percentage more than the last, income adds up while you wait, and prestige points multiply everything after a reset. Once you know them, the big questions of an idle game have exact answers. This page does the math for you: five calculators that work with the numbers any idle game shows, and how each one works, so you can check it yourself.
How to use it: you need two or three numbers from your game, such as the price of the next level, the price after buying one and your income. Type them in and the results update at once. Everything runs in your browser; nothing is sent anywhere.
What each calculator answers
| Your question | Calculator | What you need from the game |
|---|---|---|
| What will the next 10 or 50 levels cost? | Upgrade cost | the price of the next level and how much it grows |
| How long until I can buy it? | Time to afford | the price, your coins and your income |
| Which upgrade should I buy first? | Payback time | what each upgrade costs and how much income it adds |
| Is it time to prestige? | Prestige | your prestige points, what a reset gives and the bonus per point |
| What does 1.5e18 or 1ab mean? | Big numbers | any number from the game |
Upgrade cost: what the next levels will cost
In almost every idle game, each level of an upgrade costs a fixed percentage more than the level before. That percentage is the growth rate. With a growth of 1.15, every level costs 15% more than the previous one; ten levels later, the price has quadrupled. The calculator uses the standard formula idle games are built on.
The formula: the price of the next level times the growth gives the price of the level after it. Buying k levels costs price x (growth^k - 1) / (growth - 1), and the most levels your coins can buy is the largest k that still fits.
Upgrade cost calculator
Find the growth from two prices
With the example numbers, an upgrade that costs 1,000 now and grows 1.15 per level costs 20,304 for the next ten levels: about twenty times the first level's price, not ten. After those ten levels, a single level costs 4,046. With 50,000 coins you can buy 15 levels and keep 2,420.
How to find your game's growth rate
Write down the price of an upgrade, buy one level and look at the new price. Divide the new price by the old one: 1,150 / 1,000 = 1.15. Do it once more to make sure the rate stays the same from level to level. If the game only lets you buy in steps, such as x10, open the helper under the calculator: enter the price before and after and how many levels you bought in between, and it works out the rate per level.
Some games change the growth rate as you go. Idle Ronin, for example, lowers it at level 300 and again at level 1,000, so check the rate again after a big jump.
Typical growth rates
| Game | What | Growth per level |
|---|---|---|
| AdVenture Capitalist | Lemonade Stand | x1.07 |
| Idle Ronin | unit upgrade, up to level 300 | x1.14 |
| Idle Ronin | unit upgrade, levels 300 to 1,000 | x1.125 |
| Idle Ronin | unit upgrade, above level 1,000 | x1.115 |
| Idle AI Factory | factory level | x1.8 |
Small differences in growth matter enormously over many levels. At x1.07, the price doubles about every 10 levels; at x1.15, every 5; at x1.8, almost every level. That is why upgrades with a high growth rate are bought a few levels at a time, and why the last levels of a big bulk purchase are the expensive ones.
Time to afford: how long until you can buy it
The second big question in every idle game is how long to wait. The answer is the coins you still need divided by your income. The calculator turns it into hours and minutes and takes income per second, minute or hour, whichever your game shows.
Time to afford calculator
In the example, an upgrade that costs 2.5M, with 400K in the bank and 1,200 coins per second, takes 29 minutes and 10 seconds. In a real game the wait is often shorter, because your income keeps growing while you buy other upgrades. If the answer is many hours, it is usually better to buy upgrades that raise your income first; the payback calculator below tells you which ones.
Waiting offline is different: many games pay less while you are away and stop counting after a few hours. Our guide to offline earnings explains caps and rates, so you can plan a break that ends right when you can afford the upgrade.
Payback time: which upgrade to buy first
This is the most useful number in an idle game, and almost no game shows it. Payback time is how long an upgrade takes to earn back its price: its cost divided by the income it adds. The upgrade with the shortest payback time grows your income fastest, so buying in order of payback time is the quickest way through any idle game.
Example: upgrade A costs 5,000 and adds 40 coins per second, so it pays for itself in 125 seconds. Upgrade B costs 18,000 but adds 200 per second: 90 seconds. B is the better buy, even though it costs more than three times as much.
Which upgrade first? Payback time
Income per second, minute or hour, the same unit for all three. The shortest payback is the best buy.
How to read the income an upgrade adds
Many games show it on the button, such as +200/s. If yours does not, look at your total income, buy the level and look again; the difference is what it added. For upgrades that multiply, the income they add is what the boosted part already makes times the multiplier minus one: a x2 on a generator that makes 500 per second adds 500 per second.
Milestones show why this matters. The level that unlocks a x2 milestone adds as much income as the whole generator already makes, so its payback time is often far shorter than that of the levels before it. In Idle AI Factory, floors double their production at levels 10, 25, 50, 75 and 100, which is why saving for those levels pays off. Read more in how idle game progression works.
What payback time does not see
- Damage in idle RPGs. An attack upgrade does not earn coins directly. Compare upgrades by how much damage each adds per coin instead; the idea is the same.
- Unlocks. A new generator, hero or system can be worth more than its payback time shows, because it opens new upgrades.
- Events. If an event ends in an hour, an upgrade that pays back in two hours does not pay back during the event.
Prestige: how much faster a reset makes you
Prestige resets your progress in exchange for points that boost everything you do next. In most games, each point adds a fixed percentage. AdVenture Capitalist's Angel Investors add 2% profit each; in Idle Ronin, every Rebirth Token adds 10% ATK. The calculator compares your bonus now with your bonus after a reset and tells you how much faster you will be.
The formula: speed after the reset = (1 + (points you have + points from the reset) x bonus) / (1 + points you have x bonus). With 40 points, 60 from a reset and 2% per point, you go from x1.8 to x3.0, which is 1.67 times as fast.
Prestige calculator
Our rule of thumb
- x2 or more: reset now. You will be at least twice as fast, so you catch up to where you are in a fraction of the time and then go further.
- x1.5 to x2: reset when progress stalls. If you still clear a stage or buy an upgrade every few minutes, a little more time first gives you a bigger reset.
- Under x1.5: keep going. The reset gives too little to win back the time it takes to catch up.
Your first prestige is the exception: any permanent bonus beats none, so do it as soon as it unlocks. Some games multiply prestige bonuses instead of adding them, or give other rewards for a reset; there the calculator underestimates the gain. Our guide to prestige, rebirth and ascension shows the real formulas of three of our games.
Big numbers: what 1e15, 1Qa and 1aa mean
Idle numbers get so big that games shorten them. Every step is a thousand times the last: K is a thousand, M a million, B a billion, T a trillion. After that, games go different ways: names such as Qa (quadrillion) and Qi (quintillion), letter pairs such as aa and ab, or scientific notation such as 1.5e15, which means 1.5 followed by 15 digits. Type a number in any of these forms and the converter shows all of them.
Big number converter
| Number | Short | Letters | Scientific |
|---|---|---|---|
| thousand | 1K | 1K | 1e3 |
| million | 1M | 1M | 1e6 |
| billion | 1B | 1B | 1e9 |
| trillion | 1T | 1T | 1e12 |
| quadrillion | 1Qa | 1aa | 1e15 |
| quintillion | 1Qi | 1ab | 1e18 |
| sextillion | 1Sx | 1ac | 1e21 |
The letters follow the system most idle games use, with aa right after T. Not every game does: Idle AI Factory puts aa after T as here, while Idle Ronin starts letters right away, with a for a thousand. If your game's letters do not match, our guide to idle game numbers decodes the other systems.
Five mistakes these calculators help you avoid
- Buying the cheapest upgrade. Cheap is not the same as good value; the payback time decides.
- Spreading coins thinly. A milestone a few levels away often beats many levels everywhere else.
- Waiting hours for one big upgrade when two cheaper ones would raise your income and get you there sooner.
- Resetting at x1.1, or holding on at x5. Check the speed-up before every prestige.
- Misreading the numbers. 1aa is a thousand times 1T, so check big prices before you rule an upgrade out.
FAQ
How do I calculate the cost of buying max in an idle game?
Add up the levels: price x (growth^k - 1) / (growth - 1) for k levels. The upgrade cost calculator does it for you and shows the most levels your coins can buy.
What is a good growth rate for idle game upgrades?
Most upgrades grow between x1.07 and x1.15 per level, like AdVenture Capitalist's Lemonade Stand (x1.07) and Idle Ronin's units (x1.14). Fast-growing upgrades such as Idle AI Factory's factory levels (x1.8) are meant to be bought a few levels at a time.
How do I know when to prestige?
Compare your bonus now with your bonus after the reset. If the reset makes you at least twice as fast, do it; between 1.5 and 2 times, do it when progress stalls; below 1.5, keep playing. The prestige calculator works it out.
What does e mean in idle game numbers?
It is scientific notation: the number after the e tells you how many digits follow the first one. 1e15 is a 1 followed by 15 zeros, a quadrillion, and 2.5e16 is 25 quadrillion.
Do these calculators work for every idle game?
They work for any game with percentage price growth, income over time and prestige points that add up, which covers most idle and incremental games. Games with unusual rules, such as prestige bonuses that multiply, need small adjustments, and each section above says which.
Sources
- ONI Games game code: Idle Ronin (unit upgrade costs, Rebirth Tokens) and Idle AI Factory (factory levels, production milestones), September 2026.
- Anthony Pecorella, The Math of Idle Games, Part I, 2016: the Lemonade Stand in AdVenture Capitalist.
- AdVenture Capitalist Wiki, Angel Investors.
