You generally want a very thin, even layer of thermal paste—just enough to fill microscopic gaps, not enough to form a thick cushion.

Quick Scoop

  • Aim for a pea-sized dot (about 4–5 mm across) in the center of the CPU heat spreader for most desktop CPUs.
  • Typical “right amount” is roughly 0.01–0.02 ml of paste for mainstream CPUs, which visually looks like 1 small pea.
  • When you mount the cooler, its pressure will spread that dot out across the surface; you don’t need to manually smear it in most cases.

Why amount matters

  • Too little : Bare metal spots and air gaps remain, so heat can’t move efficiently to the cooler, raising temperatures.
  • Too much : The layer becomes too thick and can insulate instead of conduct, and it may squeeze out over the edges toward the socket.

A case study on a 30 mm × 30 mm CPU found that about 0.2 ml performed best among tested amounts (0.1, 0.2, 0.3 ml), with less being insufficient and more starting to hurt performance unless carefully spread.

Simple step-by-step

  1. Clean old paste from CPU and cooler with isopropyl alcohol and a lint-free cloth.
  2. Put one pea-sized drop of paste in the center of the CPU.
  1. Carefully install and tighten the cooler evenly so it spreads the paste.
  1. Do not lift and reseat the cooler without re-cleaning and reapplying paste.

Extra tips

  • For very large CPUs (HEDT, some GPUs), you might use a slightly larger dot or an “X” pattern, but the idea is still a thin, continuous film , not a blob.
  • Always replace paste when you remove the cooler—reusing the squeezed-out layer can leave voids and worse contact.

TL;DR: For “how much thermal paste on CPU,” think “tiny pea in the middle,” not “toothpaste on a toothbrush.”