Project Inputs
Rate each factor from 1 (very low) to 5 (very high). Use readiness to reflect controls already in place.
Formula Used
The calculator uses a weighted rating approach where each factor is scored from 1 to 5. A weighted average is computed, then normalized to a 0–100 scale.
- Weighted average rating: Avg = Σ(wᵢ · rᵢ) / Σ(wᵢ)
- Normalize to 0–100: Score₀ = ((Avg − 1) / 4) · 100
- Apply phase baseline: Score₁ = Score₀ · PhaseMultiplier
- Apply readiness reduction (max 40%): Final = Score₁ · (1 − 0.40 · Readiness/100)
The weekly probability and expected events are planning proxies derived from the final score.
How to Use This Calculator
- Select the project phase that matches your current work package.
- Set the planning horizon in days for your look-ahead window.
- Enter mitigation readiness based on controls already implemented.
- Rate each disturbance factor from 1 to 5 using site reality.
- Click calculate to view the score and recommended actions.
- Use the export buttons to share results with your team.
Example Data Table
Sample scenarios computed with the same weights and formula.
| Scenario | Phase | Horizon (days) | Readiness (%) | Score /100 | Band | Expected events |
|---|---|---|---|---|---|---|
| Urban trenching near traffic | Earthworks | 45 | 35 | 67.6 | High | 2.60 |
| Open-site warehouse structure | Structural | 60 | 60 | 30.8 | Low | 2.05 |
| Hospital MEP upgrade, occupied | MEP | 30 | 55 | 46.0 | Moderate | 1.32 |
| Residential finishing, stable supply | Finishing | 21 | 70 | 18.2 | Very Low | 0.55 |
| Commissioning with strict testing windows | Commissioning | 14 | 65 | 21.8 | Low | 0.40 |
View example factor ratings
| Scenario | Site congestion level | Equipment interaction intensity | Weather exposure | Ground stability/unknowns | Underground/overhead utilities risk | Public/traffic interface | Permits and inspections complexity | Material delivery volatility | Schedule compression | Crew experience risk | Noise/vibration stakeholder sensitivity | Shift/night work complexity |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Urban trenching near traffic | 4 | 4 | 3 | 4 | 5 | 5 | 4 | 3 | 4 | 3 | 4 | 3 |
| Open-site warehouse structure | 3 | 3 | 4 | 2 | 2 | 2 | 3 | 3 | 3 | 2 | 2 | 2 |
| Hospital MEP upgrade, occupied | 4 | 2 | 1 | 2 | 4 | 4 | 5 | 2 | 4 | 3 | 5 | 4 |
| Residential finishing, stable supply | 3 | 2 | 1 | 1 | 2 | 3 | 2 | 2 | 2 | 2 | 3 | 2 |
| Commissioning with strict testing windows | 2 | 2 | 1 | 1 | 3 | 2 | 4 | 2 | 4 | 2 | 2 | 3 |
Risk inputs that most often trigger disturbances
Disturbances commonly start where field uncertainty meets constrained access. High ratings for utilities risk, ground unknowns, and site congestion typically correlate with unplanned stoppages, redesigns, and resequencing. In this calculator, those drivers carry higher weights to reflect their outsized effect on work continuity. Use the factor list as a structured walk-through during daily coordination and weekly look-ahead planning.
How to read the 0–100 score bands for decisions
Treat the score as a comparative indicator between scenarios, work zones, or phases rather than a guarantee. A move from 45 to 60 is meaningful: it signals that small shocks are more likely to cascade into missed handoffs. Use the band (Very Low to Severe) to decide when to add contingency tasks, increase supervision, or revise logistics.
Phase baseline and readiness reflect real site dynamics
The phase multiplier recognizes that early work often carries more unknowns, while later phases are usually more controlled but can be time-sensitive. Readiness reduces the score when controls are already in place, such as verified service mark-outs, protected laydown zones, inspection calendars, and weather thresholds. Raising readiness by 20 points can materially reduce the final score and expected events.
Using outputs to plan buffers and control measures
Pair the weekly probability proxy with your horizon to estimate expected disturbance events and set realistic buffers. If the calculator indicates High likelihood, define a response playbook: stop-work triggers, authority for field changes, and a short list of “next best” tasks that keep crews productive. Track the score weekly and compare it to actual disruptions to calibrate ratings over time.
Example data snapshot for stakeholder reporting
The table below shows a quick export-friendly snapshot. Use it in toolbox talks, coordination meetings, and weekly reports to show how readiness and risk ratings change the forecasted disturbance intensity.
| Scenario | Phase | Readiness | Horizon | Score | Band |
|---|---|---|---|---|---|
| Urban trenching near traffic | Earthworks | 35% | 45 days | 67.6/100 | High |
| Open-site warehouse structure | Structural | 60% | 60 days | 30.8/100 | Low |
| Hospital MEP upgrade, occupied | MEP | 55% | 30 days | 46.0/100 | Moderate |
FAQs
1) What does “disturbance” mean in this calculator?
A disturbance is an unplanned interruption that changes the planned sequence, such as utility conflicts, access loss, weather stoppages, failed inspections, or material delays. It focuses on workflow impact, not only safety incidents.
2) Why are some factors weighted higher?
Weights reflect typical construction impact. Utilities and congestion often force stop-work, rework, or redesign, so they receive more influence than lower-impact disruptors. You can still compare scenarios consistently because the same weights apply to all runs.
3) How should I choose ratings from 1 to 5?
Rate the current site condition, not the plan. Use 1 for well-controlled/verified conditions and 5 for frequent conflicts or major unknowns. When unsure, align the rating to evidence: surveys, logs of delays, and inspection history.
4) What does mitigation readiness reduce?
Readiness reduces the final score by up to 40% to reflect controls already implemented. Examples include confirmed utility mark-outs, protected laydown plans, traffic management, weather thresholds, inspection bookings, and verified material lead times.
5) Is the weekly probability a true prediction?
No. It is a planning proxy derived from the score to help discuss risk over a horizon. Use it to compare alternatives and decide where to add buffers, not as a contractual forecast.
6) How often should teams recalculate?
Weekly is ideal, and again after major changes: new subcontractors, resequencing, access restrictions, permit updates, or unexpected ground findings. Track the score trend to see whether controls are improving predictability.
7) How do I use the exports effectively?
Attach CSV to weekly reports for traceable inputs and results. Use the PDF for briefings with supervisors and stakeholders. Re-export after changes so meeting notes reference the same scenario and score.