Coin limit

A coin limit is the maximum number of coins that can be collected or saved in a given area. Some courses allow infinite coins to be collected. However, in the NTSC (American) version, the coin counter is programmed to stay at the maximum of 999.

There are two types of coin limits - the 999 coin limit within the course (except Japanese version), and the 255 coin limit that is saved in the save-able records.

The 999 coin limit

The limit is intentionally put in by the programmers to prevent the game to count up coins greater than 999:

if (gMarioState->numCoins > 999) {
    gMarioState->numCoins = 999;
}

When Mario reaches the 999 coin limit, the coins are no longer counted and collecting a coin only makes noise if the value of the global timer is odd.

The 255 coin limit

Separately, there is an unintentional coin limit involving the saved coin score. This value overflows and is set to 0 if the number of coins Mario collected in the course is a multiple of 256. (Not within the course, but when recording the saved coin score after Mario exits the course.) Thus, the easiest way to obtain the highest possible saved coin score in a level is to simply collect 255 coins. 511 and 767 also produce a saved coin score of 255, but collecting more than 255 coins is not as efficient as collecting a star when 255 coins have been collected. 1,023, 1,279, etc. also save as 255, but these coin scores cannot be obtained in the NTSC version.

Coin limit for each course

Normally, the number of available coins in the course prevents the player from getting an excess number of coins to reach either of the coin limits. Nonetheless, there are ways for a player to perform infinite coin glitches such as moneybag duplication, cloning or utilizing certain exploits of the game, allowing infinite coin glitches in certain courses.

Some courses have only a finite number of coins; in these courses, cloning is impossible and there are no infinite coin glitches. The three courses that don't fall into either of these categories, namely Tick Tock Clock, Rainbow Ride, and Bowser in the Fire Sea, allow for clones to be created, but due to a lack of loading zones, the clones fill up the game's object slots. Due to this, there is a limitation on the number of coins that can be collected within these three courses.

In the table below, 999 coins represent stages with infinite coin glitches available that does not have clones occupy object slots making the game crash.

Course	Maximum Coins without coin duplication	Maximum Coins with duplication (Save-able)	Maximum Coins with duplication (within course)	Strategies
Save-able courses
Bob-omb Battlefield	146	255	999 (32767 on JP 1.0)	Breaking-Disappearing Cork Box Glitch and Ride Cancel (bob-omb cloning is possible, but limited due to object slots)
Whomp’s Fortress	141	255	999 (32767 on JP 1.0)	Breaking-Disappearing Cork Box Glitch (cork box cloning is possible, but limited due to object slots)
Jolly Roger Bay	104	104	104	No infinite coin glitches are available in this course
Cool, Cool Mountain	154	154	154	No infinite coin glitches are available in this course
Big Boo's Haunt	151	151	151	No infinite coin glitches are available in this course
Hazy Maze Cave	139	139	139	No infinite coin glitches are available in this course
Lethal Lava Land	133	133	133	No infinite coin glitches are available in this course
Shifting Sand Land	136	255	999 (32767 on JP 1.0)	Breaking-Disappearing Cork Box Glitch (bob-omb and cork box cloning is possible, but limited due to object slots)
Dire, Dire Docks	106	255	999 (32767 on JP 1.0)	Water shell cloning (going through the loading point unloads all coin clones) and cloning coin spawners
Snowman's Land	127	255	999 (32767 on JP 1.0)	Money-bag duplication and collecting a coin and enter an igloo during Time Stop on JP 1.0
Wet-Dry World	152	255	999 (32767 on JP 1.0)	Chuckya cloning (going through the loading point unloads all coin clones) and cloning coin spawners
Tall, Tall Mountain	137	255	999 (32767 on JP 1.0)	Bob-omb cloning (entering and exiting the slide unloads all coin clones) and collecting a coin and enter slide during Time Stop on JP 1.0
Tiny-Huge Island	192	255	999 (32767 on JP 1.0)	Piranha Plant glitch, collecting a coin and enter a pipe/Wiggler's cave during Time Stop on JP 1.0, Chuckya cloning and Ride Cancel
Tick Tock Clock	128	255	279	No other infinite coin glitches are available, apart from bob-omb cloning, so 279 coins is the maximum coins due to object slots
Rainbow Ride	146	255	290	No other infinite coin glitches are available, apart from bob-omb cloning, so 290 coins is the maximum coins due to object slots
Non-saveable courses
Tower of the Wing Cap	63	N/A	63	No infinite coin glitches are available in this course
Vanish Cap under the Moat	27	N/A	27	No infinite coin glitches are available in this course
Cavern of the Metal Cap	47	N/A	47	No infinite coin glitches are available in this course
The Princess's Secret Slide	80	N/A	80	No infinite coin glitches are available in this course
The Secret Aquarium	56	N/A	56	No infinite coin glitches are available in this course
Wing Mario over the Rainbow	56	N/A	56	No infinite coin glitches are available in this course
Bowser in the Dark World	80	N/A	999 (32767 on JP 1.0)	Whenever Bowser blows fire, there's a chance that some of the flames will spawn a yellow coin. Since he does this attack infinitely, you have the chance to collect infinite coins
Bowser in the Fire Sea	80	N/A	250	No other infinite coin glitches are available, apart from bob-omb cloning, so 250 coins is the maximum coins due to object slots (this Bowser doesn't blow fire that makes yellow coins)
Bowser in the Sky	76	N/A	999 (32767 on JP 1.0)	Same strategy as Bowser in the Dark World

Unbounded Coin Limit Glitch (Japanese version)

In the Japanese version, there is no coin limit within the courses. When the coin counter reaches a value of 1,000, the game runs a few lines of code wherein there is a typo:

if (gMarioState->numCoins > 999) {
    gMarioState->numLives = (s8) 999; //! Wrong variable
}

This should be the following:

if (gMarioState->numCoins > 999) {
    gMarioState->numCoins = 999;
}

Because the lives counter is a signed short, the value of 999 overflows to -25. This is displayed in the HUD as "M25". (The "M" presumably means "minus".)

After reaching a value of 32,767, the coin display remains at that value. After that, only the hidden coin count keeps incrementing. That is because the coin count is a signed short, so if the player collects more coins, the coin counter will overflow to -32,768. Since -32768 is not greater than 32,767, the coin display will not increment any further. If one were to collect a 65,636^th coin (65,536 for the overflow and 100 for the star), a second 100 coin star would spawn. This was a part of a strategy that could have been applied to collect "To the Top of the Fortress" in 0x A presses, but it wasn't because a faster 0xA strategy was discovered for that star.