The PMP exam is mostly about judgment, but you will still see calculation questions, and they are easy points if you know the formulas and, just as important, when to use each one. This cheat sheet groups every formula you need, with a short example and the trap to watch for.
Earned value basics
- PV (planned value): the budgeted cost of work scheduled to date.
- EV (earned value): the budgeted cost of work actually completed.
- AC (actual cost): what the completed work actually cost.
- BAC (budget at completion): the total budget.
| Measure | Formula | Good if |
|---|---|---|
| Cost variance | CV = EV − AC | Positive |
| Schedule variance | SV = EV − PV | Positive |
| Cost performance index | CPI = EV ÷ AC | Above 1 |
| Schedule performance index | SPI = EV ÷ PV | Above 1 |
Example. BAC $500,000, PV $200,000, EV $180,000, AC $220,000. CV = −$40,000, SV = −$20,000, CPI = 0.82, SPI = 0.90. The project is over budget and behind schedule.
Trap. EV always comes first. If you catch yourself dividing AC by EV, stop.
Forecasting: estimate at completion
This is where most people lose points, because there are four EAC formulas and the question tells you which one to use through the situation, not the numbers.
| Situation | Formula |
|---|---|
| Current cost performance will continue | EAC = BAC ÷ CPI |
| The variance was a one-off; the rest will go as planned | EAC = AC + (BAC − EV) |
| Both cost and schedule performance will continue | EAC = AC + (BAC − EV) ÷ (CPI × SPI) |
| The original estimate is no longer valid | EAC = AC + bottom-up ETC |
Related measures:
- ETC (estimate to complete) = EAC − AC
- VAC (variance at completion) = BAC − EAC
Example. Using the numbers above, if the overrun came from a one-time vendor problem, EAC = 220,000 + 320,000 = $540,000. If the team expects the same performance to continue, EAC = 500,000 ÷ 0.82 ≈ $611,000.
To-complete performance index
TCPI tells you how efficient the team must be on the remaining work.
- To finish on the original budget: TCPI = (BAC − EV) ÷ (BAC − AC)
- To finish on an approved new EAC: TCPI = (BAC − EV) ÷ (EAC − AC)
Trap. Once management approves a new EAC, the BAC version no longer applies. Read the stem for words like "approved" or "revised target".
Three-point estimating
| Method | Mean | Standard deviation |
|---|---|---|
| Triangular | (O + M + P) ÷ 3 | Not usually tested |
| Beta (PERT) | (O + 4M + P) ÷ 6 | (P − O) ÷ 6 |
Confidence ranges for a normal distribution around the mean:
- ±1 standard deviation ≈ 68%
- ±2 standard deviations ≈ 95%
- ±3 standard deviations ≈ 99.7%
Example. O = 12, M = 18, P = 36. Beta mean = 20 days, SD = 4 days. For about 95% confidence, commit to 20 + 8 = 28 days.
Schedule network
- Total float = LS − ES, or LF − EF. How far an activity can slip without delaying the project.
- Free float = ES of the successor − EF of the activity. How far it can slip without delaying the next activity.
- Forward pass gives early dates; backward pass gives late dates.
Trap. When a delay exceeds free float but not total float, the successor moves but the project end date does not.
Crashing adds resources to shorten critical activities, starting with the cheapest cost per day. Watch for near-critical paths: once two paths are equal, every further day must come off both.
Fast tracking runs activities in parallel. It adds risk, not direct cost.
Communication channels
Channels = n (n − 1) ÷ 2, where n is the number of people, including you.
Example. A team growing from 9 to 14 people goes from 36 to 91 channels, an increase of 55.
Risk and decisions
- Expected monetary value (EMV) = probability × impact. Threats are negative, opportunities positive.
- In a decision tree, calculate EMV for each branch, add the cost of the decision, and choose the best net value.
Contracts
- Cost plus incentive fee: the seller's fee changes by their share of any overrun or underrun. With an 80/20 buyer/seller ratio, the seller gains 20% of the savings.
- Point of total assumption (fixed price incentive fee) = (ceiling price − target price) ÷ buyer share + target cost.
Agile numbers
- Velocity: points completed per sprint. Use the average of recent sprints to forecast.
- Sprints remaining = remaining points ÷ velocity, rounded up, because a sprint is a whole timebox.
- Adjust for known capacity changes such as holidays before dividing.
How to use this sheet
Learn the situations as well as the formulas. The PMP exam rarely asks you to compute CPI on its own. It asks you to pick the right forecast for a story about a vendor failure, or to see that a delay exceeds free float. Practice with questions that make you choose, not just calculate.