Human Power Levels- (lowest to highest)

Muggle: This is the lowest power level and is for people who cannot do any magic or see the dementors.

Squib: This level is only slightly more powerful than a muggle, however squibs can see dementors and anti-muggle charms do not work on them.

Wizard: This is the average wizard level, they can cast all 7th year spells and can cast a few of the weakest dark arts. They can also cast around 40 of the Grey Arts. However normal wizards cannot cast the Patronous charm.

Mage: Only about 1 in 10 wizards ever become Mages, Mages are around twice as strong as a normal wizard and can cast all of the Light Arts Offensive spells, Grey Arts and all of the Dark Arts spells, they can also cast about 15 of the Black Arts. You have to be a Mage to cast a fully formed Patronous and to become an animagi. Most aurors are Mages.

High Mage: Only about 1 in 100 wizards become High Mages, High Mages are about 6 times as strong as a normal wizard or 3 times as strong as a Mage. High Mages can cast all of the spells a Mage can as well as all of the Black Arts.

Warlock: A Warlock is extremely rare, only 1 in 500 wizards are Warlocks, Warlocks are about 12 times as strong as a normal wizard or twice as strong as a High Mage. Warlocks can sometimes do basic neutral arts with out a wand and can cast the first 4 spells of the Ancient Arts (the Hammer of Thor, the Fury of Zeus, the Tridents of Neptune and the Spears of Mars). A Warlock also lives about 40 years longer than a normal wizard does.

Sorcerer: A sorcerer is even more rare than a Warlock is, only 1 in 1000 wizards are Sorcerers. Sorcerers live, on average 80 years than the normal wizard does. The most famous Sorcerer alive today is Albus Dumbledore. Sorcerers can cast all of the spells a Warlock can as well as 40 of the Forbidden Arts. They are also about 20 times stronger than a normal wizard is and can cast most of the neutral arts with out a wand.

High Sorcerer: Only about 1 in 3000 people ever become High Sorcerers, however all 4 of the Hogwarts founders were High Sorcerers. They live, on average, to be 130 years older than a normal wizard does. High Sorcerers can cast all the spells a Sorcerer can as well as all of the Ancient Arts and Forbidden Arts. High Sorcerers can cast all Light Arts Defensive Arts without a wand and a few can even cast some basic Dark Arts with out a wand. High Sorcerers are about 40 times stronger than a normal wizard is or about 2 times stronger than a Sorcerer is.

Overlord: This is extremely rare, only Magi and Avatar's can ever reach this level, two of the most famous Overlords (or Overlady's) are Merlin and Morgana Le Fey. Overlords can cast all spells, even with out a wand. In fact they are so powerful that if they did use a wand it would be destroyed from the power running through it. Overlords are about 160 times stronger than a normal human is or 3 times stronger than a High Sorcerer is. Overlords are so powerful they actually are immune to most spells and are immune to age, disease and poison, in short they are immortal.