The Power Meter is shaped like a wooden cutout of Mario's head, and it has a circle in the center where up to eight wedges are shown, each representing a unit of health. The color of every wedge depends on how many are remaining: blue for eight or seven wedges, green for five or six wedges, yellow for three or four wedges, and lastly red for two or one wedges. By default, the Power Meter is not shown onscreen unless Mario (or Yoshi, Luigi, or Wario in the remake) takes damage. Whenever the HUD shows the Power Meter, it appears at the upper-center.
There are a few different ways to refill the Power Meter, but collecting Coins is the most common method. The number of wedges that a Coin can restore in the Power Meter is relative to how many individual coins it is worth, so a regular Yellow Coin can restore one missing wedge, a Red Coin can restore two wedges, and a Blue Coin can restore five wedges. Mario can also refill the Power Meter by moving through a Spinning Heart, and the faster Mario runs through it, the more health he recovers. The Power Meter becomes fully restored whenever Mario obtains a Power Star, although this does not occur when collecting one of the Secret Stars.
The number of wedges that Mario loses from taking damage depends on how he got damaged; most enemies, such as Goombas, only cause Mario to lose a single wedge of health, while falling from a very large height depletes four wedges of health. The freezing water in Snowman's Land causes him to lose three wedges of health just from touching it. When the Health Meter reaches two sections, Mario begins to pant when standing still, but this does not affect gameplay. If Mario loses all wedges from his Power Meter, he loses a life and is forcibly exited out of whichever course he is in. If Mario loses a life at Princess Peach's Castle, he respawns in front of the castle.
The Power Meter doubles as being a breath meter while Mario is underwater, and it is shown onscreen for the entire time that he is underwater. Every several seconds, a wedge is depleted from the Power Meter. When only two sections are remaining, a soft alarm-like sound begins to play, and if Mario does not surface before the two sections run out, he runs out of air and loses a life. Even while underwater, the mechanics for the Power Meter are the same, so Mario can collect coins to regain air. If Mario resurfaces with his head above the water, he can fully regain his health, an exploit later fixed with Super Mario Sunshine's life meter, although it is retained in Super Mario 64 DS.
In Super Mario 64 DS, the Power Meter only received a few minor differences. It was redesigned to include a black border around the text and wooden profile. The profile remains in the likeness of Mario, even if Yoshi, Luigi, or Wario are being played. Furthermore, the Power Meter depletes or replenishes two or more wedges at a slower speed. The game adds a few more ways to completely refill the Power Meter, including by swapping out characters near the Rec Room or now by obtaining one of the Secret Stars. Lastly, if Mario or another character are in Toxic Gas with only one or two wedges of health remaining, the same soft alarm-like sound from underwater is played.
Slip Slidin' Away • Lil' Penguin Lost • Big Penguin Race • Frosty Slide for 8 Red Coins • Snowman's Lost His Head • Wall Kicks Will Work (N64)/Mario's Super Wall Kick (DS) • Switch Star of Cool, Cool Mountain (DS)
Big Boo's Haunt
Go on a Ghost Hunt • Ride Big Boo's Merry Go Round • Secret of the Haunted Books • Seek the 8 Red Coins • Big Boo's Balcony • Eye to Eye in the Secret Room • Switch Star of the Basement
Hazy Maze Cave
Swimming Beast in the Cavern • Elevate for 8 Red Coins • Metal-Head Mario Can Move! (N64)/Metal-Head Wario Can Move (DS) • Navigating the Toxic Maze • A-Maze-Ing Emergency Exit • Watch for Rolling Rocks • Underground Switch Star
In the Talons of the Big Bird • Shining Atop the Pyramid • Inside the Ancient Pyramid • Stand Tall On the Four Pillars • Free Flying For 8 Red Coins (5th Star, N64) (7th Star, DS) • Tox Box Switch Star (DS) • Pyramid Puzzle
Snowman's Big Head • Chill with the Bully • In the Deep Freeze (N64) • Yoshi's Ice Sculpture (DS) • Whirl from the Freezing Pond • Shell Shreddin' for Red Coins (N64) • Snowman's Silver Star (DS) • Into the Igloo • Red Coins in the House (DS)
Wet-Dry World
Shocking Arrow Lifts! • Top o' the Town • Secrets in the Shallows and Sky (N64)/5 Secrets in the Shallows and Sky (DS) • Express Elevator--Hurry Up! • Go to Town for Red Coins (N64)/Go to Town for the Red Coins (DS) • Quick Race Through Downtown! • Soaked Silver Stars (DS)
Tall, Tall Mountain
Scale the Mountain • Mystery of the Monkey Cage • Scary 'Shrooms, Red Coins • Mysterious Mountainside • Breathtaking View from Bridge (Star 5, N64)/Breathtaking View from the Bridge (Star 7, DS) • Blast to the Lonely Mushroom (Star 6, N64) (Star 5, DS) • 5 Secrets of the Mountain
Roll into the Cage (N64) • Luigi in the Cage (DS) • The Pit and the Pendulums (N64) • The Pendulum Switch Star (DS) • Get a Hand • Stomp on the Thwomp •Timed Jumps on Moving Bars • Stop Time for Red Coins • Tick Tock Silver Stars
Rainbow Ride
Cruiser Crossing the Rainbow • The Big House in the Sky • Coins Amassed in a Maze • Swingin' in the Breeze • Tricky Triangles! • Somewhere over the Rainbow • Switch Star of the Manor