Short answer
Most basketball shoes run true to size, with two consistent exceptions: Jordan (modern AJs run a half size small) and Anta / Li-Ning (international sizing runs a half size long).
Nike — TTS
Most basketball lines (Kyrie, KD, Ja, GT Cut, GT Jump, PG, Sabrina) run TTS. Lebrons run slightly roomier — true wide fitments are rare here, the looseness comes from the upper. Going down half is overkill for most users.
Jordan — half size small (modern), TTS (most retros)
Modern Jordan flagships (AJ37, AJ38, AJ39, AJ40, Luka, Tatum, Zion) run a half size small. Go up half. Air Jordan 1 retros, AJ3, AJ4 retros mostly run TTS — but it varies by colorway and production year.
Adidas — TTS, narrow lasts
Dame, Harden, AE, DON all run TTS. The Trae line runs narrower. Stripe-mounted upper construction means the laces have to do most of the lockdown work — laces tight or the shoe rotates.
Under Armour — TTS but narrow
Curry line runs TTS in length but narrow in width. Wide-footed players go up half (common) or shift brand (better).
Puma — TTS
MB and All-Pro Nitro lines TTS. Stewie line runs slightly narrow.
New Balance — slight long
TWO WAY runs about half a size long. Available in 2E and 4E width fitments — good for wide-footed players.
Anta — international half-size long
Anta sizing in US converts about half a size long. KT 9, Kai 1 — go down half. Narrow last, so wide-footed players should also go up half on width.
Li-Ning — same as Anta
Way of Wade and JB1 lines run about half a size long. Narrow forefoot. Down half.
Use the sizing helper
Our sizing helper tool gives per-brand recommended size and width call-outs based on your usual TTS size and width category.