Source: Dungeon Masters Guide

With this variant system, a character who has the Spellcasting feature uses spell points instead spell slots to fuel spells. Spell points give a caster more flexibility, at the cost of greater complexity.

In this variant, each spell has a point cost based on its level. The Spell Point Cost table summarizes the cost in spell points of slots from 1st to 9th level. Cantrips don't require slots and therefore don't require spell points.

Instead of gaining a number of spell slots to cast your spells from the Spellcasting feature, you gain a pool of spell points instead. You expend a number of spell points to create a spell slot of a given level, and then use that slot to cast a spell. You can't reduce your spell points total to less than 0, and you regain all spent spell points when you finish a long rest.

Spells of 6th level and higher are particularly taxing to cast. You can use spell points to create one slot of each level of 6th or higher. You can't create another slot of the same level until you finish a long rest.

The number of spell points you have to spend is based on your level as a spellcaster, as shown in the Spell Points by Level table. Your level also determines the maximum-level spell slot you can create. Even though you might have enough points to create a slot above this maximum, you can't do so.

The Spell Points by Level table applies to bards, clerics, druids, sorcerers, and wizards. For a paladin or ranger, halve the character's level in that class and then consult the table. For a fighter (Eldritch Knight) or rogue (Arcane Trickster), divide the character's level in that class by three. For an Artificer, add half your levels (rounded up) in the artificer class to to determine your available spell points. Homebrew

This system can be applied to monsters that cast spells using spell slots, but it isn't recommended that you do so. Tracking spell point expenditures for a monster can be a hassle.

Spell Point Cost
Spell Level Point Cost
1st 2
2nd 3
3rd 5
4th 6
5th 7
6th 9
7th 10
8th 11
9th 13
Spell Points by Level
Class Level Spell Points Max Spell Level
1st 4 1st
2nd 6 1st
3rd 14 2nd
4th 17 2nd
5th 27 3rd
6th 32 3rd
7th 38 4th
8th 44 4th
9th 57 5th
10th 64 5th
11th 73 6th
12th 73 6th
13th 83 7th
14th 83 7th
15th 94 8th
16th 94 8th
17th 107 9th
18th 114 9th
19th 123 9th
20th 113 9th