Amdahl's Law Calculator – Parallel Speedup Limit
Calculate maximum speedup from parallelization using Amdahl's Law.
About This Calculator
Calculate maximum speedup from parallelization using Amdahl's Law. Use the calculator above for instant results.
Worked Examples
- Speedup: 4x | Theoretical max: 5x
- 20% serial code limits maximum possible speedup
Answer: 4x speedup
- Speedup: 16.8x | Max: 20x
Answer: 16.8x speedup
- Max speedup is 2x regardless of core count
Answer: Max 2x — serial bottleneck
Who Uses This Calculator?
Understand parallel computing limits.
Design parallel systems effectively.
Identify parallelization bottlenecks.
Demo parallel scaling law.
Common Mistakes to Avoid
❌ Assuming all code can be parallelized
Amdahl's Law shows even a 5% serial portion caps speedup at 20x regardless of how many processors you add.
❌ Communication overhead not included
Real parallel systems have synchronization and communication overhead. Actual speedup is often less than Amdahl predicts.
Frequently Asked Questions
Amdahl's Law formula?
Speedup = 1 / ((1-P) + P/n). Where P = parallel fraction, n = processors.
Gustafson's Law alternative?
Gustafson's Law takes a different approach: as problem size grows, more work can be parallelized. More optimistic than Amdahl.
When does Amdahl's Law apply?
Fixed workload that you want to run faster. For scaling workloads, Gustafson's Law is more appropriate.