LBO Modeling Basics

A leveraged buyout is, mechanically, a simple idea: buy a company using mostly debt, use the company's own cash flow to pay that debt down, and sell it a few years later for more equity than you put in. The math behind that idea is what every PE interview technical is actually testing: not whether you can build a spreadsheet, but whether you understand what makes the equity value grow.

Entry: sizing the deal

Everything starts with Enterprise Value:

Entry EV = Entry EBITDA × Entry Multiple

A sponsor doesn't pay for that entirely in cash. A typical buyout finances 55-65% of the purchase with debt, with the rest coming from sponsor equity (plus, often, a slice of management rollover, existing management reinvesting part of their own sale proceeds into the new structure, which aligns their incentives with the sponsor's).

Debt = Entry EV × Debt %
Sponsor Equity = Entry EV − Debt − Rollover Equity

Sponsor equity is always the last line solved, never an input: it's the plug. If it comes out negative, the deal is either over-levered or over-priced relative to what a lender will finance.

The debt schedule: where the return actually gets built

This is the part a lot of candidates skip past too quickly. Each year, the company generates EBITDA, pays interest on its outstanding debt, pays taxes, and whatever cash is left over (the cash sweep) goes straight to paying down principal ahead of schedule:

Interest Expense = Beginning Debt Balance × Interest Rate
Taxes = MAX(0, (EBITDA − Interest Expense) × Tax Rate)
Cash Available for Sweep = EBITDA − Interest Expense − Taxes
Ending Debt = MAX(0, Beginning Debt − Cash Available for Sweep)

Two things worth internalizing here. First, interest is calculated on the beginning balance, not some blended average, in the simplest version of this model. Real models sometimes average beginning and ending balance instead, which introduces circularity (see below). Second, taxes are floored at zero: if interest expense exceeds EBITDA in a bad year, the company doesn't get a negative tax bill, it just pays none.

This is also where a specific interview trap lives: if a deal deleverages fast enough, the debt balance can hit exactly $0 before the hold period ends. A well-built model needs that MAX(0, ...) floor, or ending debt goes negative, which is nonsensical (the company doesn't start earning interest just because a term loan paid off).

Why LBO models are often circular

Notice that interest expense depends on the beginning debt balance, which is safe, non-circular. But if a model instead computes interest off the average of beginning and ending balance (a common refinement for accuracy), then interest depends on ending debt, which depends on the cash sweep, which depends on interest. That's a genuine circular reference. The two standard fixes: turn on iterative calculation in Excel (with a "circularity breaker" switch so a broken formula doesn't spiral into a #REF! loop that's hard to debug), or simply calculate interest off the beginning balance only: the standard simplification for a timed interview exercise, since the precision loss is small relative to how much faster it is to build cleanly.

Exit: converting deleveraging into equity value

At the end of the hold period, the company is sold at (usually) the same or a different multiple:

Exit EV = Exit EBITDA × Exit Multiple
Exit Equity = Exit EV − Ending Debt

The entire return story compresses into two numbers:

MoIC = Exit Equity ÷ Sponsor Equity
IRR = MoIC ^ (1 / Hold Years) − 1

The three return drivers: the question every interviewer actually wants answered

A 3.0x MoIC over five years can come from wildly different deals, and being able to decompose why a deal returned what it did is the real skill being tested:

1. Deleveraging: Entry Debt minus Exit Debt, funded entirely by the company's own free cash flow, not new sponsor capital. This is the most repeatable driver: a stable, cash-generative business with modest capex will delever reliably even with flat EBITDA.
2. EBITDA growth: (Exit EBITDA − Entry EBITDA) × Entry Multiple. Real operating improvement: revenue growth, margin expansion, cost-out.
3. Multiple expansion (or compression): Exit EBITDA × (Exit Multiple − Entry Multiple). The least controllable driver, since it depends on market conditions at exit, not anything the sponsor did.

Summing those three deltas plus entry equity should roughly reconcile to exit equity. When an interviewer asks "where did this return come from," they're asking you to run exactly this decomposition, and a deal that returned 3x purely on multiple expansion is a much riskier, less repeatable story than one that returned 3x mostly through deleveraging.

What makes a good LBO candidate

Not every business supports this structure. The characteristics lenders and sponsors actually screen for: predictable, recurring free cash flow (to service and pay down debt); low ongoing capex relative to EBITDA; a defensible market position (a lender won't finance a company at real risk of demand collapsing); and headroom in the existing capital structure. Cyclical, capital-intensive businesses are difficult LBO candidates precisely because leverage amplifies the downside exactly when EBITDA is falling and the debt is hardest to service.

The mental model to leave with: an LBO isn't really about debt; debt is just the lever. The actual work is buying a business whose own cash flow can carry that lever, and the return is the mathematical consequence of how well it does.