---
id: external-drives.why-does-the-speed-test-give-different-results
url: https://storagestudio.us/faq/external-drives/why-does-the-speed-test-give-different-results
category: "External drives"
subcategory: "Speed, cables and hardware"
question: "Why does the drive speed test give different results each time?"
alt_questions:
  - "Benchmark results vary"
  - "Speed test slower the second time"
  - "Inconsistent read write speeds external SSD"
  - "drive benchmark numbers change"
  - "Why is my SSD slower than advertised?"
  - "Speed test lower than the box says"
short_answer: "Speeds vary with how full and warm the drive is, other activity on it such as Spotlight, and the port and cable. Makers quote best-case numbers. Close other apps, connect directly and run the test twice for a fair reading."
tags: ["speed test", "benchmark", "performance"]
related: ["https://storagestudio.us/faq/external-drives/do-external-ssds-get-hot", "https://storagestudio.us/faq/external-drives/how-does-the-drive-speed-test-work", "https://storagestudio.us/faq/external-drives/should-i-plug-the-drive-into-a-hub-or-directly"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# Why does the drive speed test give different results each time?

Real drives don't run at one fixed speed. Results shift with how full the drive is, how warm it is, whether something else is reading or writing to it at the same moment (Spotlight indexing, a backup, an open app), and the port, hub and cable in use. Drive makers usually quote best-case figures, so everyday results are often lower.

For a fair comparison, close apps using the drive, connect it directly with a good cable and run **Run benchmark** a couple of times. Storage Studio's verdict cares about whether the drive is comfortably fast enough, not about small differences between runs.