📖 Overview
Use this tool to quantify race performance progress over training cycles.
🧪 Example Scenarios
Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.
| Input | Base Case | Higher Pressure Case |
|---|---|---|
| Old Time | 100 | 120 |
| New Time | 115 | 138 |
⚙️ How It Works
This measures relative movement from an old value to a new value as a percentage of the old value.
The Formula
Change % = [(New − Old) ÷ Old] × 100
| New | The new or current value |
| Old | The original or reference value |
| Change | Positive = increase, Negative = decrease |
💡A 20% gain followed by a 20% loss does not return to the original — it results in a 4% net loss. Percentage change is direction-sensitive and asymmetric.
Quick Reference
| Old Value | New Value | Change % |
|---|---|---|
| 100 | 120 | +20% |
| 100 | 80 | −20% |
| 250 | 300 | +20% |
| 1,000 | 850 | −15% |
| 50 | 100 | +100% |
When To Use This
- Use this tool when you need a fast decision during active planning or execution.
- Use this before committing money, time, or tradeoffs that are hard to reverse.
- Use this to compare options using the same assumptions across scenarios.
Edge Cases To Watch
- Results can be misleading if key inputs are missing, stale, or unrealistic.
- Very small or very large values may amplify rounding effects and interpretation risk.
- If assumptions change mid-decision, recalculate before acting.
Practical Tips
💡 Use consistent units for both inputs.
💡 Positive and negative values indicate direction of change.
💡 Pair this with absolute change for better context.
Frequently Asked Questions
❓ Why not only use absolute difference?
Percentage normalizes change across different base values.
❓ Can this be used for revenue or weight?
Yes, it works for any comparable numeric series.