Amdahl Parallel Speedup Calculator
Estimate fixed-workload speedup from parallel fraction, worker count and entered constant overhead.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Keep the workload fixed, divide only the parallelizable runtime by workers and add entered overhead.
Tnew/Tbase=(1−p)+p/n+overhead; speedup=Tbase/Tnew; efficiency=speedup/n
Worked example
90% parallel work and four workers with zero overhead give relative runtime 0.325, speedup≈3.07692308 and efficiency≈76.9230769%. The ideal infinite-worker limit is 10×.
Assumptions and input details
Parallel share is 0–100%, workers 1–1e6, overhead 0–1000% of baseline and baseline time positive. Overhead is a constant entered fraction applied even at one worker; it is not inferred from communication or worker count. Perfect splitting of the parallel fraction is assumed. Fixed-workload Amdahl scaling is distinct from growing-workload Gustafson scaling and measured benchmark speedup.
References: Cornell: Amdahl law
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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