The PM Math Cheat Sheet: Essential Formulas for Waterfall & Agile (2026 Guide)
15+ Project Management Formulas Every PM Must Know to Succeed
1. The Waterfall Powerhouse: Earned Value Management (EVM)
In Waterfall, predictability is king. EVM is the gold standard for measuring performance by comparing the work actually performed against the plan.
Core EVM Formulas
|
Metric |
Formula |
What it tells you |
|---|---|---|
|
Cost Variance (CV) |
EV - AC |
Are you over or under budget? (Positive is good) |
|
Schedule Variance (SV) |
EV - PV |
Are you ahead or behind schedule? (Positive is good) |
|
Cost Performance Index (CPI) |
EV / AC |
For every $1 spent, how much work are you getting? |
|
Schedule Performance Index (SPI) |
EV / PV |
At what rate are you progressing compared to the plan? |
Forecasting Formulas
- Estimate at Completion (EAC): BAC / CPI (Use this to predict the total cost based on current performance.)
- To-Complete Performance Index (TCPI): (BAC - EV) / (BAC - AC) (This tells you how efficiently you must work from now on to stay within budget.)
2. Planning and Estimation (Waterfall)
Before the project even starts, you need to estimate how long tasks will take.
PERT (Program Evaluation and Review Technique)
PERT uses a weighted average to give a more realistic time estimate than a simple guess.
- Formula: (Optimistic + 4*Most Likely + Pessimistic) / 6
Critical Path Method (CPM)
While less of a "math formula" and more of a logic flow, calculating the Float (or Slack) is vital:
- Total Float: Late Start (LS) - Early Start (ES) (If the float is 0, the task is on the Critical Path.)
3. The Agile Pulse: Velocity and Flow
Agile doesn't care about "Earned Value" in the traditional sense. Instead, it focuses on the speed of value delivery.
Velocity
Velocity is the average amount of work (usually in Story Points) a team completes in a Sprint.
Calculation: Total Story Points Completed / Number of Sprints
Burndown and Burnup
These charts help you visualize if the team will finish the scope on time.
Burndown Rate: Remaining Work / Remaining Time
Flow Metrics (Kanban/Scrum)
- Cycle Time: The time it takes for a task to go from "In Progress" to "Done."
- Lead Time: The time from the moment a request is made until it is "Done."
- Work in Progress (WIP) Limit: A cap on the number of items in a specific state to prevent bottlenecks.
4. Financial Success Metrics (Universal)
Every PM should speak the language of the business. These formulas help justify why your project should exist in the first place.
- Return on Investment (ROI): (Net Profit / Cost of Investment) * 100
- Payback Period: Total Investment / Annual Cash Inflow
- Cost-Benefit Ratio: Total Benefits / Total Costs
Pro-Tips for 2026 Project Management
- Don’t do math in your head: Use tools like Jira, Asana, or Smartsheet to automate these. Your job is to interpret the numbers, not just calculate them.
- Context is Queen: A CPI of 0.8 is bad, but if it was 0.5 last month, you’re actually improving. Always look at the trend, not just the snapshot.
- Human Buffer: Formulas don't account for "burnout." Always add a 10-15% contingency buffer to your time estimates to account for the unexpected.
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