📖 Overview
This calculator converts your plan into a clear on time risk signal.
It combines expected travel delay pressure and early arrival preference into one slack number.
Use it before meetings interviews airport departures and appointments where late arrival has real cost.
🧪 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 |
|---|---|---|
| Estimated Travel Time (min) | 35 | 42 |
| Expected Delays (min) | 15 | 18 |
| Minutes Until Deadline | 70 | 84 |
| Desired Early Arrival Buffer (min) | 10 | 11.5 |
⚙️ How It Works
Estimates whether your schedule has enough slack to arrive before a hard deadline with low lateness risk.
The Formula
Slack = Time Until Deadline − (Travel Time + Expected Delays + Desired Early-Arrival Buffer)
| Time Until Deadline | Minutes remaining until your fixed start time |
| Travel Time | Base no-disruption travel estimate |
| Expected Delays | Likely friction from traffic, transit waits, parking, security, etc. |
| Early Buffer | Minutes you want to arrive before start time |
💡Positive slack means you still have margin. Negative slack means your current plan is already late under the entered assumptions.
Quick Reference
| Scenario | Slack | Interpretation |
|---|---|---|
| 70 deadline, 35 travel, 15 delays, 10 buffer | +10 min | Moderate safety margin |
| 55 deadline, 35 travel, 15 delays, 10 buffer | -5 min | High late risk |
| 90 deadline, 40 travel, 20 delays, 15 buffer | +15 min | Low late risk |
| 45 deadline, 30 travel, 12 delays, 8 buffer | -5 min | Leave immediately |
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
💡 If slack is negative, leave now and reduce uncertainty sources.
💡 Use conservative delay estimates for flights interviews and client meetings.
💡 Recalculate when conditions change, not just once before leaving.
Frequently Asked Questions
❓ What does negative slack mean?
Your current plan is likely late unless conditions improve.
❓ Is this predictive AI?
No, this is a deterministic timing model using your assumptions.