Your luck affects many aspects of the game (see below) and is actually the sum of two components: regular luck and bonus luck. Regular luck, which is always from -10 to 10, changes with events in the game, and may slowly return to a baseline level (See "Luck timeout" below). Bonus luck, on the other hand, may be -3, 0, or +3 and is determined by what kind of luckstone (and certain artifacts) you are carrying. Thus the highest possible total luck is 13, and the lowest possible is -13. A positive value indicates a measure of "good luck" and a negative value indicates "bad luck". However, only a rough idea of your total luck is given in the enlightenment list; the meaning of the messages is as follows:
|<= -10||extremely unlucky|
|-9 to -5||very unlucky|
|-4 to -1||unlucky|
|0||luck is zero (wizard mode only)|
|1 to 4||lucky|
|5 to 9||very lucky|
|>= 10||extremely lucky|
Luck timeout refers to your regular luck slowly returning to zero over time, which it will do under normal circumstances. If your luck is timing out, it is done at a rate of one point per 600 moves (300 if you are carrying the Amulet of Yendor, or if your god is angry). This is counted from the beginning of the game; for example, if you lose one point of Luck on turn 590, you will regain it on turn 600, not on turn 1190.
The baseline level to which it may return is +1 if you most recently started or restored the game during a full moon, -1 if started/restored on Friday the 13th, and 0 if neither or both. A new moon does not affect your Luck at all. These changes in the baseline level do not affect the maximum and minimum values.
Whether your regular luck will return to its baseline level is controlled by luckstones and certain Quest Artifacts. The effect of these "luck items" depends on the number in your main inventory that are blessed, uncursed, and cursed (see table below).
|Number of luck items||Bad Luck||Good Luck|
|None||Times out||Times out|
|More cursed than blessed||No timeout||Times out|
|Equal cursed and blessed (or all uncursed)||No timeout||No timeout|
|More blessed than cursed||Times out||No timeout|
Note that as a special case (which is possibly a bug), the game will consider you to own no luck items if both the following conditions are true:
- You have no luckstones, specifically;
- The number of cursed luck items (other than stones) equals the number of noncursed luck items.
When this case applies, the effect is identical to owning no luck items: no bonus luck, and luck times out regardless of whether the total is positive or negative.
Bonus luck works in a similar way to the above table, although both blessed and uncursed luck items (referred to as "non-cursed") have the same effect.
|Number of luck items||Bonus luck|
|More cursed than non-cursed||-3 "reduced luck"|
|Equal cursed and non-cursed||+3 "extra luck"|
|More non-cursed than cursed||+3 "extra luck"|
The same caveats regarding having the same number of cursed as noncursed luck items and no luckstones apply here as to luck timeout.
Ways to change your Luck
Regular Luck is adjusted by each of the events described below, and by the timeout described above. It cannot be reduced below -10 or increased above +10.
|Baseline Luck Adjustment||Event|
|+1||Starting or restoring a game during a full moon.|
|0||Starting or restoring a game during any time when it is neither full moon nor Friday the 13th, or when it is both full moon and Friday the 13th (which cancel each other out).|
|-1||Starting or restoring a game on Friday the 13th.|
|Regular Luck Adjustment||Event|
|-2||Break a mirror. (Other glass items have no effect on Luck.)|
|-n||Breaking n eggs laid by you (at worst -5).|
|+1||Sitting on a throne (sometimes).|
|0||Throwing a worthless gem at a unicorn.|
|-1 to +1 (averages to 0)||Throwing unknown valuable gem at cross-aligned unicorn.|
|-3 to +3 (averages to 0)||Throwing known valuable gem at cross-aligned unicorn.|
|+1||Throwing unknown valuable gem at co-aligned unicorn.|
|+2||Throwing named valuable gem at co-aligned unicorn.|
|+5||Throwing identified valuable gem at co-aligned unicorn.|
|-1||Hitting a blind floating eye (1 in 500 chance).|
|-1/0*||Jumping in Sokoban.|
|-1/0*||Breaking a boulder in Sokoban.|
|-1/0*||Casting stone-to-flesh on a Sokoban boulder.|
|-1/0*||Polymorphing a Sokoban boulder.|
|-1/0*||Reading a scroll of earth in Sokoban.|
|-1/0*||Being pulled by a thrown iron ball in Sokoban.|
|-1/0*||Hurtling through the air in Sokoban due to Newton's 3rd Law. (i.e. throwing something while levitating)|
|-1/0*||Squeezing past a boulder in Sokoban (or walking over one when polymorphed into a giant)|
|-1||Killing a tame monster.|
|-1||Killing a peaceful monster (sometimes). See note below.|
|-2||Killing a peaceful human when you are not chaotic. ("You murderer!")|
|-5||Killing a co-aligned unicorn.|
|-5 to -2||Cannibalism (eating your own species), unless an orc or a caveman.|
|Set to 0||Praying with negative regular luck (sometimes: "golden glow" boon).|
|-3||Praying on wrong altar.|
|-3||Praying before your prayer timeout has expired.|
|-5||A sacrifice (not your own race) on Moloch's altars in Gehennom.|
|-3||Being converted by trying to convert an altar.|
|-1||Otherwise unsuccessful at converting altar.|
|+1||Successfully converting an altar.|
|-1||Sacrificing at another god's altar.|
|-1||Kicking another god's altar ("Thou shalt pay, infidel!")|
|-1||Trying to engrave something on another god's altar (also gives "Thou shalt pay, infidel!")|
|+2||Sacrificing your own race on your own chaotic altar.|
|-2||Sacrificing your own race on Moloch's altar.|
|-5||Sacrificing your own race when you aren't chaotic.|
|-1||Sacrificing an unidentified fake Amulet of Yendor.|
|-3||Sacrificing an identified fake Amulet of Yendor.|
|+1||Sacrificing, slightly mollifying your god, negative luck.|
|Set to 0||Sacrificing, mollifying your god, negative luck.|
|+1||Sacrificing, having a hopeful feeling, negative luck.|
|Set to 0||Sacrificing, reconciling, negative luck.|
|0 to +5||Sacrificing, god happy.|
- As of Nethack 3.6.0, any luck penalty associated with Sokoban only applies on levels that haven't been fully solved yet.
Note about luck penalty for killing peaceful monsters, from :
If you manage to kill a peaceful monster without angering it, you have a 50% chance of losing one point of Luck. This is in addition to the Luck penalty for murder described above and the penalty of -5 Luck for killing a unicorn of your own alignment. However, simply killing a peaceful monster with one whack from a melee weapon will anger it before it dies, avoiding this penalty. Most wands and spells will also anger a monster even if they kill it in one zap, but "beam" attacks such as striking or polymorph have a chance of killing without angering, and incurring the additional penalty.
A drawbridge can also kill a peaceful without angering it.
Luck in-game effects
Luck has a part in:
- Making a monster peaceful by untrapping it
- Making a (too heavy to lift) monster peaceful by trying to untrap it ("<monster> thinks it was nice of you to try.")
- Getting an alignment bonus for untrapping a monster
- Accidentally setting off a landmine or beartrap that you are trying to set
- Having monsters get mad when they are trapped by one of your traps
- Setting off a trap you are trying to disarm
- Disarming a shooting trap
- Having chest traps fail to work (flame fizzles out, etc)
- Having chest traps that do work limited to relatively minor effects (especially if you have a unicorn horn)
- Getting any result from prayer (except upset gods—Luck < 0 causes this)
- Getting help from your god when poorly aligned
- Getting a good result from prayer
- Getting the full range of bonus results from prayer
- Being confronted by a minion of the god of the altar you converted (or tried to)
- Causing the gods to be angry when praying in Gehennom
- Having angry gods being less fire and brimstone in their approach
- Hitting a monster
- Hitting a monster with a thrown object
- Hitting a monster with an iron ball when it jerks you back (?)
- Hitting something with a boomerang without it splintering
- Getting good things from thrones (Luck < 0 is sometimes bad, Luck > 0 is sometimes good)
- Destroying/getting gold and gems from throne (Luck >= 5 maximises number of gems)
- Getting good things from a magic fountain (natural luck >= 0 required; natural luck >= 4 desirable)
- Finding secret doors, corridors and traps.
- Breaking open a door
- Opening a door
- Having your objects resist water damage
- Blessed metal items resisting rust
- Having a wand of wishing succeed (Luck >= 0 guarantees this)
- Getting what you wish for (Luck >= 0 is pretty much essential)
- Writing a scroll you don't know
- Picking something off the floor by applying your whip
- Attempting a teleport spell in need (guaranteed if Luck >= 1)
- Getting at least 2 identifies from a blessed scroll of identify (Luck > 0)
- Having destroyed polymorphed objects create golems
- Having a split off long worm remain tame/peaceful
Natural Luck refers to your luck without taking the bonus (or penalty) luck from carrying a luckstone into account. Most effects of luck include this bonus, but a handful do not and directly check your luck stat:
- Effects of a magic fountain
- Getting a wish from a throne
- Clones of tame or peaceful monsters remaining tame or peaceful
- Anything that checks your luck for the purpose of changing it, e.g. praying with negative luck to have it reset to 0.
Most luckstone/luck item strategy is presented in the article on luckstones.
As a quick summary, though: you can't do any better than one blessed luck item, so you might as well keep any others in a bag (where they have no effect) as spares in case your main one is cursed. Even an uncursed luck item will be just as good except when your total luck is negative (which is a rare situation, although not unheard of); and even when it is negative, the luckstone will harm you only on turns on which your luck would time out (so you can just bag it for those turns). Cursed luckstones should never be kept in main inventory unless doing so is unavoidable.
UnNetHack adds an additional artifact, Luck Blade, that affects luck timeout. In UnNetHack, luck items greatly slow down luck timeout rather than stopping it completely. The modified luck timeout depends on how far your luck is from your base luck: the higher or lower your luck, the less the timeout is slowed. The timeout is calculated every turn, meaning gaining or losing a point of luck could result in that point timing out immediately. This also means that luck timeout is no longer necessarily at multiples of 600 turns if your natural luck has ever been above or below your base luck.
The modified luck timeout is calculated by the following formula. Let lnatural be your current natural luck, lbase be your base luck, and a be 2 if you have the Amulet or your god is angry with you, or 1 otherwise. 
||lnatural – lbase|||Timeout||Time to 0||Time from 9||Time from 10||Time from 11|
|0||∞||0||168 000||173 000||173 800|
|1||24 800||24 800||143 200||148 200||149 000|
|2||24 200||49 000||119 000||124 000||124 800|
|3||23 200||72 200||95 800||100 800||101 600|
|4||21 800||94 000||74 000||79 000||79 800|
|5||20 000||114 000||54 000||59 000||59 800|
|6||17 800||131 800||36 200||41 200||42 000|
|7||15 200||147 000||21 000||26 000||26 800|
|8||12 200||159 200||8 800||13 800||14 600|
|9||8 800||168 000||0||5 000||5 800|
|10||5 000||173 000||0||0||800|
If you have the Amulet or your god is angry with you, halve all times in this table.
This page is based on a spoiler by Dylan O'Donnell. The original license is:
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