Estimating Benefits
Estimate the performance improvements for your project.
Quick Estimation
| Project Type |
Expected Speedup |
| Small (< 100 files) |
1.5-3x |
| Medium (100-1000 files) |
2-5x |
| Large (> 1000 files) |
3-10x |
| Monorepo with sharing |
5-20x |
Factors
Positive Factors
- Large number of targets
- Frequent incremental builds
- Team sharing (remote cache)
- Branch switching
- CI/CD pipelines
Neutral Factors
- Already fast builds (< 10s)
- Single developer
- Always-changing inputs
Calculation
Time Saved = (Builds/day) × (Avg build time) × (1 - 1/Speedup)
Example:
- 20 builds/day
- 5 minute average
- 3x speedup
- Saved: 20 × 5 × (1 - 1/3) = 67 minutes/day
Test Your Project
# Current (ninja)
time ninja
# Clean rebuild
ninja -t clean
time ninja
# With rninja
time rninja
# Clean + cached
rninja -t clean
time rninja
# Check cache hits
rninja -t cache-stats
ROI Estimation
| Metric |
Value |
| Developer hourly cost |
$X |
| Time saved per day |
Y minutes |
| Developers |
N |
| Annual savings |
X × Y/60 × N × 250 |