How are spells spread across levels?
Low levels dominate: 24 cantrips and 49 1st-level spells, but only 15 spells at 9th level.
The pyramid is steep. Nearly half the list sits at cantrip through 2nd level, which is why low-level casters still feel spoiled for choice. At the top end, 9th-level magic is a short and famous list — 15 spells in the whole SRD.
For character building, that means breadth comes early and identity comes late: two wizards can look interchangeable at level 3 and completely different at level 17.
Which school of magic is biggest?
Evocation leads the SRD with 60 spells; Necromancy is the smallest school.
Evocation (60 spells) and Transmutation (59) together account for a large share of the entire list — the game simply has more ways to alter and conjure than to do anything else.
School size matters more than it looks: abilities that key off a school (a wizard’s Savant features, magic resistance quirks, counterspell rulings at some tables) are effectively stronger the bigger their school is.
How much of the list needs concentration?
39% of all SRD spells (126 of 319) require concentration — the real limit on caster power.
Concentration is the quiet balance mechanism of 5e: no matter how many powerful ongoing effects you know, you can maintain exactly one. With roughly a third of the list gated behind it, spell selection is less about the best spell and more about the best spell per concentration slot.
Rituals run the other way: 29 SRD spells carry the ritual tag and can be cast without spending a slot at all, ten minutes at a time. A ritual caster mines that list for free utility.