"Walk me through how you'd value the synergies in this deal" is one of the most common follow-up prompts in M&A and valuation interviews. Candidates who just multiply a synergy estimate by a discount factor tend to miss half the credit available. Here is the full method interviewers are actually listening for.
Step 1: Separate Revenue Synergies from Cost Synergies
Never model synergies as one blended number. Revenue synergies (cross-selling, bundling, pricing power) and cost synergies (headcount overlap, procurement savings, facility consolidation) behave differently and need to be estimated, risk-adjusted, and phased separately. Start by listing each synergy source individually with a standalone run-rate estimate — the annual dollar value once the synergy is fully realized.
Step 2: Risk-Adjust Each Synergy for Realization Probability
Multiply each run-rate estimate by a probability of realization. Cost synergies typically get a higher probability (70-80%) because management controls the execution directly. Revenue synergies get a lower probability (40-60%) because they depend on customer and market response. The formula is simple: Risk-Adjusted Synergy = Run-Rate Synergy × Probability of Realization. Skipping this step — or worse, applying the same probability to both types — is one of the fastest ways to lose credibility with an interviewer.
Step 3: Phase the Synergies Over a Realistic Timeline
Synergies are never captured on day one. Systems need to be integrated, contracts renegotiated, and sales teams cross-trained. Apply a ramp schedule — for example 30% of the run-rate in Year 1, 65% in Year 2, and 100% by Year 3 — to each risk-adjusted synergy stream. Cost synergies usually ramp faster than revenue synergies, since layoffs and contract renegotiations can happen quickly, while cross-selling relationships take longer to build.
Step 4: Convert Revenue Synergies to Their EBITDA Impact
This is the step candidates most often forget. Cost synergies drop straight to EBITDA — a dollar saved is a dollar of EBITDA. Revenue synergies do not: the incremental revenue still carries a cost of delivering it, so you need to apply a gross margin assumption. EBITDA Impact from Revenue Synergies = Phased Revenue Synergy × Gross Margin. Only after this conversion can you add the revenue synergy's EBITDA contribution to the cost synergy's EBITDA contribution for a true combined total.
Step 5: Discount the Combined Stream to Present Value
Once you have a total EBITDA synergy figure for each year, discount each year's value back to today using the deal's discount rate (typically the acquirer's WACC): NPV of Synergies = Σ [Total EBITDA Synergy (Year N) / (1 + Discount Rate)^N]. The resulting NPV is the maximum synergy premium the acquirer can justify paying above the target's standalone value without destroying shareholder value.
See the Full Method Worked Through With Numbers
Reading the steps is one thing — running the actual numbers is what makes this stick. Synergy Case: Revenue and Cost walks through this exact five-step method with a full worked example: a $20m revenue synergy and a $15m cost synergy, risk-adjusted at different probabilities, phased over a three-year ramp, and discounted to a final present value. For the related methodology on taxing synergies before discounting them, see Synergy Valuation.
Once you're comfortable with synergy valuation, the natural next step is seeing how these figures feed into a full deal model — see Full Accretion/Dilution Analysis for how synergy assumptions determine whether a deal is EPS-accretive or dilutive.