What Does a CPU Benchmark Actually Measure?
A CPU benchmark measures how quickly a processor can complete a specific computational task. The challenge is that "CPU performance" is not a single number — a CPU that excels at single-threaded integer arithmetic may be mediocre at multi-threaded floating-point operations, and vice versa.
Different benchmark tools measure different things, and the scores are not directly comparable between tools. Understanding what each benchmark measures helps you choose the right tool for your use case.
Browser-Based Benchmarks (CPUKiller)
CPUKiller's CPU Benchmark tool runs four tests in your browser using JavaScript Web Workers: integer arithmetic, floating-point operations, memory bandwidth, and cryptographic hashing.
What it measures: JavaScript engine performance — which is a combination of CPU capability and browser JIT compiler efficiency. A V8-based browser (Chrome, Edge) will score differently than SpiderMonkey (Firefox) on the same hardware.
When to use it: Quick performance checks, comparing performance across browser updates, testing systems where you cannot install software, and getting a rough sense of relative CPU performance.
Limitations: Browser benchmarks cannot access hardware directly. They measure JavaScript performance, not raw CPU throughput. Results vary by 10–20% between browsers on the same hardware.
Cinebench — The Rendering Standard
Cinebench (currently R23 and 2024) renders a complex 3D scene using the Cinema 4D rendering engine. It tests both single-core and multi-core performance separately.
What it measures: CPU rendering performance — specifically, how quickly the CPU can complete ray-tracing calculations. This correlates well with performance in 3D rendering, video encoding, and other multi-threaded workloads.
Single-core score: Reflects the performance of one CPU core. This correlates with gaming performance, since most games are still primarily single-threaded.
Multi-core score: Reflects total throughput across all cores. This correlates with rendering, encoding, and compilation performance.
When to use it: Comparing CPUs for content creation workloads, validating overclocks, and comparing against published benchmarks for purchasing decisions.
Geekbench — Cross-Platform Comparison
Geekbench runs on Windows, macOS, Linux, iOS, and Android, making it the best tool for cross-platform CPU comparisons. It tests a wide range of workloads including cryptography, image processing, machine learning, and memory performance.
What it measures: A broad range of real-world workloads, weighted to reflect typical usage patterns. The scores are calibrated against a reference machine (a Mac mini with an Intel Core i7).
When to use it: Comparing a Windows PC against a Mac, comparing desktop CPUs against mobile processors, and checking performance against published Geekbench scores for purchasing decisions.
PassMark — The Value Benchmark
PassMark's PerformanceTest suite includes a CPU benchmark that tests integer math, floating-point math, compression, encryption, and physics simulation. PassMark maintains a database of results from millions of users, making it easy to compare your CPU against a large reference set.
When to use it: Checking where your CPU ranks against a large database of results, identifying whether a CPU is performing as expected, and getting a quick overall performance score.
Benchmark Score Comparison
| Tool | Measures | Platform | Free |
|---|---|---|---|
| CPUKiller | JS engine performance | Browser | Yes |
| Cinebench R23 | 3D rendering | Win/Mac | Yes |
| Geekbench 6 | Mixed workloads | All platforms | Yes (online) |
| PassMark | Mixed workloads | Win/Mac/Linux | Yes |
| AIDA64 | CPU + system | Win | Trial |
Which Benchmark Should You Use?
For a quick check without installing anything: use CPUKiller's browser benchmark. For comparing against published scores for a purchasing decision: use Cinebench R23 (content creation) or Geekbench 6 (cross-platform). For a comprehensive system audit: use PassMark PerformanceTest. For overclock validation with stress testing: use AIDA64 or Prime95.
No single benchmark tells the complete story. For important decisions, run two or three different tools and compare the results.