The PMP exam has fewer calculations than many people fear, but the ones it has are reliable marks if you know them cold. Here is every formula worth memorising, grouped by topic, each with a quick example. For an interactive version and a calculator, see the free PMP formulas page.
Earned value: the core
Use one example throughout: budget at completion (BAC) $560,000; planned value (PV) $280,000; earned value (EV) $252,000; actual cost (AC) $315,000.
| Formula | Meaning | Example |
|---|---|---|
| CV = EV − AC | Cost variance. Negative = over budget | 252 − 315 = −$63k |
| SV = EV − PV | Schedule variance. Negative = behind | 252 − 280 = −$28k |
| CPI = EV ÷ AC | Cost efficiency. Below 1 = over budget | 252 ÷ 315 = 0.80 |
| SPI = EV ÷ PV | Schedule efficiency. Below 1 = behind | 252 ÷ 280 = 0.90 |
The trick: EV always comes first. Subtract for a variance, divide for an index.
Forecasting
| Formula | Use it when | Example |
|---|---|---|
| EAC = BAC ÷ CPI | Current cost performance will continue | 560 ÷ 0.8 = $700k |
| EAC = AC + (BAC − EV) | The variance was a one-time event | 315 + 308 = $623k |
| EAC = AC + new ETC | The original estimate was wrong | Re-estimate the rest |
| EAC = AC + (BAC − EV) ÷ (CPI × SPI) | Cost and schedule both affect the rest | 315 + 308 ÷ 0.72 ≈ $743k |
| ETC = EAC − AC | Money still to spend | 700 − 315 = $385k |
| VAC = BAC − EAC | Expected over/under at the end | 560 − 700 = −$140k |
| TCPI = (BAC − EV) ÷ (BAC − AC) | Efficiency needed to finish on budget | 308 ÷ 245 ≈ 1.26 |
More detail in earned value formulas explained and the free chapter Plan and Manage Finance.
Estimating
- Three-point (beta / PERT): (O + 4M + P) ÷ 6. With O = 6, M = 9, P = 18 weeks: (6 + 36 + 18) ÷ 6 = 10 weeks.
- Triangular: (O + M + P) ÷ 3. Same numbers: 33 ÷ 3 = 11 weeks.
- Standard deviation (beta): (P − O) ÷ 6. Here (18 − 6) ÷ 6 = 2 weeks.
Schedule
- Float = LS − ES (or LF − EF). Critical path activities have zero float.
- Critical path = the longest path through the network = the shortest possible project duration.
Worked example: critical path and float.
Communication and risk
- Communication channels: n(n − 1) ÷ 2. A team of 9 has 9 × 8 ÷ 2 = 36 channels.
- Expected monetary value: probability × impact. A 25% chance of a $36,000 loss has an EMV of −$9,000.
Contracts
- CPIF fee: target fee + seller's share × (target cost − actual cost). Under target, the fee rises; over target, it falls. See contract types.
How to remember them
- Write the sheet from memory every morning for a week.
- Do five calculation questions a day. The free flashcards include a formulas deck.
- On the exam, write nothing down until you understand what the question asks. Most formula questions are really "which formula fits this situation" questions.