This online test drives controlled CPU load in your browser and measures throughput and responsiveness in real time. It runs locally, is not a hardware or thermal benchmark, and reports what the page can sustain under different settings.
How it works
Threads
Defines how many parallel workers run. Each worker is a busy loop. More threads try to occupy more CPU cores.
Example: If you set 8 threads on an 8-core CPU, the load spreads across cores. If you set more than your cores, the OS will time-slice threads and they will compete.
Duration
Controls how long the run lasts. Preset options: 30, 60, 180 seconds, or indefinite until you stop manually.
Mode
Chooses what kind of arithmetic is used in the loops. Each stresses different CPU execution units.
- Balanced: Mixes integer and floating-point math. Represents a general workload like many everyday programs.
- Integer: Performs prime number checks. This hammers integer logic and branching units. It is light on memory but intense for the integer pipelines.
- Float: Performs small matrix multiplications. This stresses floating-point/vector units (FPU/SIMD). It mimics workloads like graphics shaders or scientific code.
The differences matter because some CPUs are faster in integer math, others in floating-point, and mixing both shows overall balance.
Session Controls
- Start: begins with a short baseline (to measure early stable throughput) then runs the chosen load.
- Stop: ends the run immediately.
- Pause/Resume: lets you freeze and continue a run.
- Export: produces a JSON file with settings and results.
- Theme: switches dark/light styling.
- Advanced: reveals fine-tuning options.
Advanced Options
Target Load
Workers don’t always run 100% of the time. Target load sets the duty cycle:
- 100% = workers run nonstop.
- 75%, 50%, 25% = workers run for part of each time window and rest for the remainder.
- Auto = tool adjusts the duty dynamically to keep performance stable and reduce lag.
Ramp Up
Instead of launching all threads at once, adds them gradually (one per second). Lets you see how throughput and responsiveness change as load rises.
Multi-Phase Profile
Splits the run into phases (light at start, full in the middle, lighter at end). Shows how the system recovers when the load shifts.
Pause on Tab Hide
Ends or pauses runs when the browser tab is hidden. Prevents misleading results from background-tab throttling.
Progress
The bar fills as the run advances. During baseline it moves slowly, during active run it tracks percent done.
Live Metrics
- Estimated CPU Load (Gauge)
An inferred % of CPU saturation. It blends how much work was requested, how much was achieved, and how delayed the system is. Color shifts: green (ok), amber (warning), red (critical). - Elapsed / Remaining
How long the test has been running and how much is left. - Ops / Sec
How many operations per second workers complete. Smoothed to avoid flickering. - Total Ops / Average
Cumulative operations plus the average rate so far. - Responsiveness
Measures how much scheduled timers are delayed (lag). If a timer meant to fire at 100 ms actually fires at 110 ms, responsiveness shows +10 ms. Low numbers mean the browser remains snappy; high numbers mean the event loop is congested. - Threads (Live vs Target)
Shows how many workers are currently active compared to what you asked for. - Peak Ops/Sec & Consistency
Peak = highest throughput sample. Consistency = stability of throughput over time.- Very Steady: near constant.
- Steady: mild fluctuations.
- Variable: noticeable swings.
- Highly Var: large, unstable swings.
- Relative vs Baseline
Current throughput as % of early baseline. Useful to detect throttling — if it falls far below 100%, something slowed down. - Achieved Load
The actual fraction of time workers were active. This shows if workers met their target duty. Example: If you asked for 75% duty but achieved only 60%, the system was too busy to keep up. - Throttle Suspect
Flags “Possible” when two things happen together: throughput falls below about half of baseline and timer lag spikes. This often signals OS or thermal throttling.
Recent Ops/Sec Trend
A bar sparkline of recent throughput samples. Lets you see short-term dips and spikes.
Metric Guide
Definitions are listed at the bottom of the tool for quick reference:
- Ops / Sec = throughput
- Responsiveness = lag in timers
- Achieved Load = actual duty ratio
- Consistency = stability of throughput
- Throttle Suspect = heuristic for throttling
Test Summary and History
After a run ends, a summary line shows settings and results: duration, threads, mode, average and peak ops/sec, and relative % vs baseline. Guidance notes point out variability or lag issues. Session history keeps the last few runs for comparison. Export outputs the results in JSON format.
What are your results on your device? Would You like to see any more features in this test? Let us know in the comments!
CalcuLife.com
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