Small whole “baby” or mini potatoes usually take about 20–30 minutes at 400°F (200°C), depending on size and how crowded your pan is.

Quick time guide

  • Very small bite‑size potatoes (about 1 inch): 20–25 minutes at 400°F until fork‑tender.
  • Small baby potatoes (up to 1½ inches): 25–35 minutes at 400°F, checking after 20 minutes.
  • Small whole russets (5–6 oz each): 35–40 minutes at 400°F if baked like classic jacket potatoes.

Simple method

  • Toss small potatoes with a bit of oil, salt, and any seasonings, then spread in a single layer on a baking sheet.
  • Bake at 400°F, turning once halfway, and start testing at the earlier time by piercing with a knife; they are done when it slides in easily with little resistance.

Quick doneness checks

  • Skin should look slightly blistered or crisp, and the inside should feel very soft when poked.
  • If they are not quite tender at the minimum time, keep baking in 5‑minute increments until done, since oven temps and potato size vary.

Bottom line: for most small potatoes at 400°F, plan on roughly 20–30 minutes for baby potatoes and around 35–40 minutes for small full russets, always confirming with a fork or knife test.